Creator media glossary
What is an SRT file?
Short answer
A SubRip subtitle file (.srt): plain text that lists numbered captions, each with a start and end time, which a player or platform shows over the video.
Key takeaways
- An SRT file is a plain-text caption file: numbered cues, start and end times, and text.
- Timestamps use a comma before the milliseconds: 00:00:01,500.
- YouTube and Facebook accept SRT caption uploads; save as UTF-8.
- Burn captions in where a platform does not take caption files.
SRT file explained
An SRT file is the simplest caption format in common use. Each caption is a block of three parts: a number, a timing line such as 00:00:01,600 --> 00:00:04,200 (hours, minutes, seconds and milliseconds after a comma), then one or two lines of text. A blank line ends the block.
Because it is only text and timing, an SRT opens in any text editor and is accepted by most players and many platforms as a separate "sidecar" file. It carries no reliable styling or position, so captions that must look a certain way, or appear on platforms that do not take caption files, are burned into the video instead.
Where SRT came from
SRT is named after SubRip, a free Windows program from around 2000 that read the subtitles burned into DVD video with optical character recognition and saved them as text with timings. The format was so simple that players, editors and platforms adopted it, and it is still the most widely supported caption file.
SRT format, line by line
- A cue number, counting from 1.
- The timing line: start --> end as hours:minutes:seconds,milliseconds, for example 00:01:02,500 --> 00:01:05,000. The separator before the milliseconds is a comma.
- One or two lines of caption text. Many players also read <b>, <i>, <u> and <font color> tags, but platforms such as YouTube ignore styling.
- A blank line, then the next cue.
Save the file as plain text in UTF-8 so accented letters, emoji and non-Latin scripts survive.
Caption file formats YouTube supports
From YouTube Help. The basic formats need only timing and text; the advanced ones add styling or position.
| Format | Extension | What YouTube supports |
|---|---|---|
| SubRip | .srt | Basic files only, no styling; plain UTF-8 |
| SubViewer | .sbv or .sub | Basic files only, no styling; plain UTF-8 |
| WebVTT | .vtt | Positioning supported; styling limited to bold, italic, underline |
| TTML / DFXP | .ttml, .dfxp | Partial: styling and positioning supported |
| SAMI | .smi or .sami | Timecodes, text and simple markup; no positioning |
SRT vs VTT
Both are plain text with one cue per caption. A VTT file starts with the line WEBVTT, uses a full stop before the milliseconds (00:00:01.600) and can place each caption on screen; an SRT uses a comma (00:00:01,600) and has no reliable position or style. Converting between them is a matter of rewriting the header and timestamps.
SRT vs VTT vs ASS
| SRT | VTT | ASS / SSA | |
|---|---|---|---|
| Full name | SubRip | Web Video Text Tracks | Advanced SubStation Alpha |
| Styling | Basic tags in some players | CSS via STYLE blocks, bold, italic, underline | Full: fonts, colors, outlines, animation |
| Positioning | No | Yes (cue settings, regions) | Yes, per line |
| Used by | Almost every player and upload form | Browsers, HLS, YouTube | Fansubs, karaoke, styled burn-ins |
| YouTube upload | Yes | Yes | Not listed |
Free tools:SRT vs VTT comparedASS captions
How to create an SRT file
- Windows: write the cues in Notepad, then File > Save as, choose "All files", name it captions.srt and pick UTF-8 encoding.
- Mac: in TextEdit choose Format > Make Plain Text before typing, then save with the .srt extension.
- Faster: generate captions automatically (YouTube, Premiere Pro, DaVinci Resolve and CapCut transcribe speech) and export SRT, then correct names and timing.
- Keep each caption to two short lines and on screen long enough to read.
Free tool:SRT caption guide by platform
How to open or add an SRT file
- Read or edit it in any text editor.
- Play it with a video in VLC (Subtitle > Add Subtitle File) or IINA; giving the SRT the same name as the video loads it automatically.
- QuickTime Player does not load separate SRT files; use VLC or convert the captions.
- Upload it as a caption track on YouTube and Facebook, or burn it into the picture for platforms that do not take caption files.
Free tool:Burned-in captions
Common SRT problems
- Strange characters (é, ?): the file was saved in a legacy encoding; re-save as UTF-8.
- Captions slowly drift out of sync: they were timed for a different frame rate (25 fps vs 23.976); retime proportionally in a subtitle editor.
- All captions early or late by the same amount: shift every timestamp with a subtitle editor or a sync offset.
- Upload rejected: a missing blank line, a full stop instead of the comma in a timestamp, or overlapping cues.
Frequently asked questions
What is an SRT file?
A SubRip subtitle file: plain text listing numbered captions, each with a start and end time and one or two lines of text. Players and platforms read it as a separate caption track.
What does an SRT file look like?
Each caption is a number on its own line, a timing line such as 00:00:01,600 --> 00:00:04,200 (a comma before the milliseconds), the caption text, and a blank line before the next caption.
Does YouTube accept SRT files?
Yes. YouTube supports basic SRT files in plain UTF-8; styling markup in the file is ignored, and YouTube suggests SRT or SBV if you are new to caption files.
How do I add an SRT file on Facebook?
Facebook takes captions as SubRip (.srt) files: edit the post, choose Add captions, then Upload captions and pick the .srt file. Repeat for each language.
Should I upload an SRT or burn the captions in?
Upload an SRT where the platform takes caption files, so viewers can turn captions on or off. Burn captions in for platforms or placements that do not take files, or when the style must stay fixed.
Can I convert SRT to VTT?
Yes: add a WEBVTT line at the top and change the comma before the milliseconds to a full stop in every timestamp. Cue numbers can stay. Subtitle editors and our caption guides do it for you.
What is the difference between closed and open captions?
Closed captions are a separate track, such as an SRT, that viewers can switch on or off. Open (burned-in) captions are part of the picture and always visible.
Let Koldflux pick the settings
Koldflux chooses the codec, container and bitrate for each platform when it exports.
Free tools that use this
Sources and how we checked
- YouTube Help: Supported subtitle and closed caption files (checked 2026-10-05)
- Facebook Help: Add captions to a video you upload to your profile (checked 2026-10-05)
- MDN: Web Video Text Tracks Format (WebVTT) (checked 2026-10-05)
Reviewed October 5, 2026 by the Koldflux team. Definitions follow the specifications and platform documentation linked above; platform tables come from the same registry the Koldflux tools use.