SRT (SubRip) is the most widely supported subtitle format: plain text with a sequence number, a timestamp range, and the caption text. It works with YouTube, VLC, and nearly every player and editor.

What's the difference between SRT and WebVTT?

Both are text-based. WebVTT (VTT) adds web-friendly features like styling, positioning, and cue settings — it's the standard for HTML5 video. SRT is simpler and more universally supported offline.

Can AddSub generate subtitle files?

Yes. AddSub transcribes and translates live audio and can export the result as SRT or TXT, ready to attach to any video.

Subtitle File Formats Explained: SRT, VTT, ASS, and More

The short answer: SRT is the format to use 95% of the time — it’s plain text, universally supported (YouTube, VLC, editors). WebVTT is the web standard for HTML5 video. ASS adds advanced styling for fan-subs. Here’s when to use each.

The formats at a glance

Format	Extension	Best for
SubRip	.srt	Universal — YouTube, VLC, editors, phones
WebVTT	.vtt	HTML5 web video, styling & positioning
Advanced SubStation	.ass	Advanced styling, karaoke, fan-subs
Plain text	.txt	Transcripts, search, quick reference

What an SRT file looks like

1
00:00:01,500 --> 00:00:04,000
Welcome to today's AddSub demo.

2
00:00:04,500 --> 00:00:07,000
Everything is processed on-device.

Each block = sequence number + timestamp range + caption. That’s the whole format.

SRT vs WebVTT vs ASS — when to use what

SRT — upload to YouTube, play in VLC, burn into videos. If in doubt, use SRT.
WebVTT — adding captions to your own HTML5 video player; supports cue styling, positioning, and chapters.
ASS — only if you need heavy styling (fonts, colors, karaoke). Overkill for most.
TXT — a plain transcript; no timing, great for search and reference.

How to generate them automatically

You don’t have to type subtitles. AddSub transcribes any audio playing on your Mac in real time — in 99 languages — and can export the result as SRT or TXT with perfect timing. It also translates live, so you can generate subtitles in a different language from what’s spoken, all 100% on-device.

Generate SRT subtitles automatically — free for 7 days

No payment needed to start. Download for macOS.