ESL: Expressive Subtitle Language

ESL is an open-source initiative defining a rich, human-readable subtitle format designed for expressive and dynamic text presentations. It leverages the clarity of HCL (HashiCorp Configuration Language) to provide a comprehensive framework for timed text, intricate styling, complex motion effects, and karaoke.

Key Features

• Expressive Styling: Hierarchical styles, per-cue overrides, fine-grained control over fonts, colors, borders, shadows, and alignment.
• Advanced Motions: Define reusable, multi-property animations (opacity, position, scale, rotation, shear) with various easing functions and precise timing.
• Karaoke Support: Built-in syntax for word-by-word or syllable-by-syllable text reveal.
• Human-Readable Syntax: Based on HCL, making files easy to write, read, debug, and version control.
• Structured & Modular: Logical organization into meta, style, motion, and cue blocks promotes maintainability.
• Extensible: Designed with future enhancements in mind.

Specification

The definitive guide to the ESL format, its syntax, and semantics can be found in the official specification:

➡️ Read the ESL Specification (Version 1.1)

➡️ PDF Format

This document details all available blocks, attributes, data types, and conventions for creating valid ESL files.

Examples

A simple ESL file (example.esl):

meta {
title="Simple Demo"esl_version="1.1"resolution=[1920, 1080]
default_style="default"
}
style"default" {
font_family="Arial"font_size=48color="#FFFFFF"align="bottom-center"shadow=[2, 2, 3, "#00000080"]
}
motion"fade_in_quick" {
duration=300opacity=1
}
cue {
in=1000out=5000opacity=0text="Hello, World!"style="default"motion_in=["fade_in_quick"]
}