VTT Validator
VTT Input
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Validation Results
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About VTT Validator
Our VTT Validator is a powerful, free online tool that ensures your VTT (WebVTT) files meet proper format standards and timing requirements. WebVTT is the web standard for displaying timed text tracks alongside HTML video elements. Our validator checks syntax, timestamps, WebVTT header compliance, and provides detailed feedback to help you create perfect web-compatible subtitle files.
What is VTT Format?
VTT (WebVTT - Web Video Text Tracks) is the W3C standard format for displaying captions, subtitles, descriptions, chapters, and metadata for HTML5 video elements. Developed specifically for web use, VTT files provide enhanced features like styling, positioning, and metadata support while maintaining simplicity and broad browser compatibility.
VTT Format Specification
Standard VTT Structure:
WEBVTT
NOTE
Optional note or comment
00:00:00.000 --> 00:00:03.500
First caption text appears here
00:00:03.500 --> 00:00:07.200
Second caption follows
STYLE
::cue { color: white; }VTT Validation Features
- WebVTT Header: Validates required "WEBVTT" file signature
- Timestamp Format: Checks HH:MM:SS.mmm --> HH:MM:SS.mmm structure
- Cue Validation: Verifies proper cue block formatting
- Note Blocks: Validates optional NOTE sections
- Style Blocks: Checks CSS styling syntax
- Time Accuracy: Ensures chronological order and valid values
VTT Advanced Features
Cue Settings: Positioning and alignment options (line, position, size, align).
CSS Styling: Custom styling with ::cue pseudo-element.
Voice Labels: Speaker identification with <v Speaker> tags.
Text Formatting: Bold, italic, underline, and color markup.
NOTE Blocks: Comments and metadata within the file.
REGION Blocks: Advanced positioning and scrolling areas.
VTT Timestamp Format
Time Format
- • Format: HH:MM:SS.mmm or MM:SS.mmm
- • Hours: optional, 00-99
- • Minutes: 00-59 (two digits)
- • Seconds: 00-59 (two digits)
- • Milliseconds: 000-999 (three digits)
Cue Timing
- • Separator: " --> " (space-arrow-space)
- • Start time comes first
- • End time comes second
- • Optional cue settings after timing
- • Example: 00:01:30.500 --> 00:01:33.200
Why Choose VTT for Web Video?
VTT is the official web standard for HTML5 video captions and subtitles. It offers superior features compared to other formats when used on the web, including native browser support, advanced styling capabilities, positioning controls, and metadata support. VTT files are essential for web accessibility compliance and provide the best user experience for online video content.
Supported Browsers & Platforms
Web Browsers: Chrome, Firefox, Safari, Edge, Opera (all modern versions)
Video Platforms: YouTube, Vimeo, HTML5 video players, JW Player
Media Libraries: Video.js, Plyr, MediaElement.js, Flowplayer
CMS Platforms: WordPress, Drupal, Joomla with video plugins
Mobile Browsers: iOS Safari, Chrome Mobile, Samsung Internet
VTT vs Other Formats
VTT Advantages
- • Native browser support
- • Advanced styling capabilities
- • Positioning and alignment
- • Web accessibility standard
- • Metadata and comments support
Best Use Cases
- • HTML5 video websites
- • Online learning platforms
- • Streaming web applications
- • Accessibility compliance
- • Progressive web apps
Best Practices for VTT Files
- Always start with the "WEBVTT" header on the first line
- Use UTF-8 encoding for international character support
- Keep caption lines under 32 characters for mobile readability
- Maintain 1-3 second minimum display time for each cue
- Test with multiple browsers to ensure compatibility
- Use semantic markup for better accessibility
- Consider using NOTE blocks for file documentation