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Use FormDatasubmitter parameter - #29028

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jenseng:use-formdata-submitter
Dec 18, 2025
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Use FormDatasubmitter parameter#29028
eps1lon merged 1 commit into
react:mainfrom
jenseng:use-formdata-submitter

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@jensengjenseng commented May 8, 2024•
edited by eps1lon
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Summary

Fixes#29018
Fixes#34944
Closes#34990
Closes#35354

Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.

Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:

Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:

constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill

Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.

How did you test this change?

Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.

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Comparing: 454fc41...a497924

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

Generated by 🚫 dangerJS against a497924

@jenseng

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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628

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The two browsers which we support that were the main culprits before was:

  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.

Once those are confirmed, we can move to the submitter parameter.

@jenseng

jenseng commented May 8, 2024

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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?

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jensengforce-pushed the use-formdata-submitter branch 2 times, most recently from bb3ec87 to e33216eCompareMay 16, 2024 16:11
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@github-actionsgithub-actionsBot added the Resolution: Stale Automatically closed due to inactivity label Aug 14, 2024
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bump

@github-actionsgithub-actionsBot removed the Resolution: Stale Automatically closed due to inactivity label Aug 14, 2024
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jensengforce-pushed the use-formdata-submitter branch from 05f1fc3 to bb0ab71CompareAugust 22, 2024 17:08
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This pull request has been automatically marked as stale. If this pull request is still relevant, please leave any comment (for example, "bump"), and we'll keep it open. We are sorry that we haven't been able to prioritize reviewing it yet. Your contribution is very much appreciated.

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bump

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bump 🥲

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bumpity bump

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Another bug caused by the current partial polyfill: #34944

cc @sebmarkbage

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eps1lonforce-pushed the use-formdata-submitter branch from b1117e6 to a497924CompareDecember 18, 2025 10:22
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.

@eps1lon
eps1lon merged commit 65eec42 into react:mainDec 18, 2025
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UseFormDatasubmitterparameter (#29028)
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Bug: Form submitter is missing, if form includes input with name 'id' Bug: Incorrect form data when using an image submit button

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@jenseng@react-sizebot@sebmarkbage@eps1lon@facebook-github-bot
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
Skip to content
Use FormDatasubmitter parameter - #29028
Merged
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
Dec 18, 2025
Merged
Use FormDatasubmitter parameter#29028
eps1lon merged 1 commit into
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jenseng:use-formdata-submitter
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@jenseng
@jensengjenseng
commented
May 8, 2024•

edited by eps1lon

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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
@react-sizebot
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

Generated by 🚫 dangerJS against a497924
@jenseng
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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
@sebmarkbage
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
@jenseng
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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bumpity bump
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
@eps1lon
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


5 participants

@jenseng@react-sizebot@sebmarkbage@eps1lon@facebook-github-bot

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
Skip to content
Use FormDatasubmitter parameter - #29028
Merged
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
Dec 18, 2025
Merged
Use FormDatasubmitter parameter#29028
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
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@jensengjenseng
commented
May 8, 2024•

edited by eps1lon

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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
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Use FormDatasubmitter parameter - #29028
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Use FormDatasubmitter parameter#29028
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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
@jenseng
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


5 participants

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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
Skip to content
Use FormDatasubmitter parameter - #29028
Merged
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
Dec 18, 2025
Merged
Use FormDatasubmitter parameter#29028
eps1lon merged 1 commit into
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jenseng:use-formdata-submitter
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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
Skip to content
Use FormDatasubmitter parameter - #29028
Merged
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
Dec 18, 2025
Merged
Use FormDatasubmitter parameter#29028
eps1lon merged 1 commit into
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May 8, 2024•

edited by eps1lon

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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

Generated by 🚫 dangerJS against a497924
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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
@sebmarkbage
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
@jenseng
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


5 participants

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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
Skip to content
Use FormDatasubmitter parameter - #29028
Merged
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
Dec 18, 2025
Merged
Use FormDatasubmitter parameter#29028
eps1lon merged 1 commit into
react:mainfrom 
jenseng:use-formdata-submitter
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May 8, 2024•

edited by eps1lon

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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
Use `FormData` `submitter` parameter by jenseng · Pull Request #29028 · react/react · GitHub
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Use FormDatasubmitter parameter - #29028
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Use FormDatasubmitter parameter#29028
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Summary
Fixes#29018
Fixes#34944
Closes#34990
Closes#35354
Rather than continuing to maintain/fix an incomplete polyfill (e.g. #28056, #34990), just pass the submitter to the FormData constructor, since it is now widely available. This ensures that the form data is populated consistently with a native form submission, and lets us remove a whole lot of code. This is a followup to this discussion over two years ago.
Elaborating on that, if we're concerned about browsers that don't support it, it's important to note that:
Older browsers (Safari on old iOS, Samsung TVs), can polyfill FormData the way React did:
constOriginalFormData=globalThis.FormDataclassFormDataWithSubmitterPolyfillextendsOriginalFormData{constructor(form,submitter){console.log(form,submitter)if(submitter!=null){consttemp=submitter.ownerDocument.createElement('input');temp.name=submitter.name;temp.value=submitter.value;if(form.id){temp.setAttribute('form',form.id);}submitter.parentNode.insertBefore(temp,submitter);super(form)temp.parentNode.removeChild(temp)}else{super(form)}}}globalThis.FormData=FormDataWithSubmitterPolyfill
Note that the above doesn't apply to native submissions but neither did React's behavior. It only applied to React's Form Actions.
How did you test this change?
Updated an existing test to more fully cover submitter serialization, and ran yarn test and yarn test --prod successfully.
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Comparing: 454fc41...a497924
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=608.16 kB607.60 kB=107.67 kB107.54 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=667.39 kB666.83 kB=117.55 kB117.42 kB
facebook-www/ReactDOM-prod.classic.js=693.47 kB692.91 kB=122.05 kB121.92 kB
facebook-www/ReactDOM-prod.modern.js=683.89 kB683.34 kB=120.43 kB120.31 kB
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-experimental/react-dom/unstable_server-external-runtime.js=18.59 kB18.15 kB=4.19 kB4.13 kB

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Looks like flow needs a fix: https://github.com/facebook/flow/blob/b75ba641223ff7fe597d43ca8d4ae76c52efe9f9/lib/bom.js#L628
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The two browsers which we support that were the main culprits before was:
  1. Safari on older iOS versions that still wasn't updated to latest version. Safari takes a surprisingly long time to actually propagate. It's not enough that an iOS version is released.
  2. Older Samsung TVs with web UIs. E.g. Facebook has TV apps on those.
Once those are confirmed, we can move to the submitter parameter.
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@sebmarkbage just curious, is there a test matrix or something to automatically validate that? or is it more of a manual process/judgment call?
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Another bug caused by the current partial polyfill: #34944
cc @sebmarkbage
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We think it's fine to remove this. Browsers without support for the second arg can restore the original behavior by polyfilling FormData.
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Bug: Form submitter is missing, if form includes input with name 'id'

Bug: Incorrect form data when using an image submit button


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