Troubleshooting: Caption file types

This article contains specifications for each common caption file type. If you are experiencing errors with your captions, check to make sure your file meets the requirements below.
In this article:

• WebVTT
• SRT

WebVTT

Specs:

• Files must begin with a valid signature (WEBVTT)
• Timecode is represented as 00:00:00.000
• Cues often (but do not have to) include a numeral identifier (e.g. 1, 2, 3, ...)
• Cues must have a content line (even if empty) followed by a break line

SRT

Specs:

• Files must begin with the first cue's numerical identifier (e.g. 1, 2, 3, ...)
• Timecode is represented as 00:00:00,000 
  • Hours, minutes, and seconds are always written as two characters (07 not 7).
    Milliseconds are always written as three characters.
• Cues must have a content line (even if empty) followed by a break line