SRT subtitle format — complete reference
Overview
SRT (SubRip Subtitle) is the world's most widely supported subtitle format. Introduced by the SubRip software in 1999, it remains the default choice for desktop video players, editing tools and YouTube uploads.
- Extension:
.srt - Encoding: usually UTF-8
- Structure: cue-based, plain text
- Header: none
Structure
Each cue has three parts, separated by a single blank line from the next cue:
1 00:00:01,000 --> 00:00:04,000 This is the dialogue. 2 00:00:05,500 --> 00:00:08,750 Second cue's dialogue.
Timing format
Timestamps use HH:MM:SS,mmm. Milliseconds are separated by a comma. Both start and end timestamps use the same format, separated by --> (dash-dash-greater-than).
Theoretically the hour field is variable length, but by convention it is two digits zero-padded. Sub-second precision is milliseconds (three digits).
Cue numbering
Cue numbers are sequential integers starting from 1. Most players do not require them to be strictly sequential — but breaks in the sequence cause problems in some players and make manual editing harder.
Use the Cue Renumbering tool to fix broken numbering in a file.
Supported HTML tags
SRT supports a small set of HTML-like tags for inline styling:
<i>...</i>— italics<b>...</b>— bold<u>...</u>— underline<font color="#...">...</font>— text color
Support for these tags varies between players. WebVTT supports a different, more restricted set. When converting between formats, tags can become unbalanced or dropped.
Common problems
- Wrong millisecond separator. Commas, not periods. Periods are for WebVTT.
- Missing blank lines. Each cue must be separated from the next by exactly one blank line.
- Missing cue numbers. While some players accept cues without numbers, most expect them.
- BOM characters. Some editors add a UTF-8 BOM that a few players reject. Use the Encoding Cleaner.
- Invalid encoding. Non-UTF-8 encodings produce garbled text.
- Overlapping cues. Technically allowed but often indicates a timing mistake.
- Cues out of order. Not fatal but confusing to edit.
Working with SRT on this site
This site has 25 free tools for working with SRT and other subtitle files: