What is vtt format

Overview

VTT stands for Web Video Text Tracks, also known as WebVTT. It is an open standard format developed by the World Wide Web Consortium (W3C) for creating and displaying captions, subtitles, and cue points in web video content. Unlike older caption formats, VTT is designed specifically for web video and integrates seamlessly with HTML5 video elements.

File Structure and Format

A VTT file is a plain text file beginning with the header 'WEBVTT'. Each caption or subtitle is defined with a timestamp range in the format [hh]mm:ss.xxx --> [hh]mm:ss.xxx followed by the text content. Multiple cues can be included in a single file, each with their own timing and text. The simple text-based format makes VTT files easy to create, edit, and parse by both humans and software.

Styling and Customization

WebVTT supports basic styling and formatting through tags similar to HTML. Developers can use styling for colors, fonts, background colors, and text positioning. The format also supports CSS styling through the VIDEO::cue pseudo-element, allowing for advanced customization that matches a website's design. Cues can also include voice identification and note information for accessibility.

Web Integration

VTT tracks are embedded in HTML5 using the <track> element within <video> tags. This provides native browser support without plugins or external JavaScript libraries. Modern web browsers automatically recognize and display VTT captions and subtitles, making it the standard format for accessible web video. Streaming platforms like Netflix and YouTube use WebVTT internally.

Use Cases

WebVTT is used for multiple purposes including video captions for accessibility compliance, multi-language subtitles for international audiences, speaker identification in educational videos, and chapter markers. The format is compatible with most modern video players, content management systems, and streaming services.