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SRT vs VTT vs ASS: which subtitle format should you use?
By Himanshu Ranjan · Updated 8 November 2026
Use SRT for the widest compatibility, WebVTT for HTML5 web video, ASS when you need styling and positioning, LRC for synced song lyrics and TTML for broadcast and streaming workflows. FileDial converts between several of them on your Mac, offline, with the original kept.
SRT, the common denominator
SubRip (SRT) is plain text: a counter, a timing line using hours:minutes:seconds,milliseconds with a comma, then the text. Styling tags like bold and italic are unofficial extensions. There is no official encoding, so the character set can vary. Nearly every player and editor reads it, which makes it the safe default.
WebVTT, the web's format
WebVTT is the W3C format for the HTML5 track element. It is based on SRT but needs a WEBVTT header, uses full stops in timestamps, requires UTF-8, makes cue numbers and hours optional, and adds comments, metadata, chapters and cue settings, with styling through CSS. Choose it for your own site's video player. See the SRT to VTT guide.
ASS, when looks matter
SubStation Alpha, in its ASS form, supports styling, positioning and karaoke effects and is used by tools such as Aegisub. It is a good fit for fansub-style typography. It is less widely supported by simple players, and FileDial's note on converting to ASS says styling is not carried over from the source, so you will style it in an editor afterwards.
SBV, LRC and TTML
SBV is the YouTube format, available in FileDial through Convert › Convert to SBV (YouTube). LRC is a lyrics format, with [mm:ss.xx] time tags, paired with a song file of the same name, available as Convert › Convert to LRC lyrics. TTML is XML-based, a W3C standard used in broadcast and streaming, available as Convert › Convert to TTML.
Converting between them in FileDial
Select the subtitle file in Finder and pick from Convert: Convert to SRT, Convert to WebVTT, Convert to ASS, Convert to SBV (YouTube), Convert to LRC lyrics or Convert to TTML. Each saves a new file beside the original. Styling, meaning fonts, colours and positions, is not carried over, so keep your richest source file as the master. Convert › Convert to plain text gives words only.
Choosing by destination
YouTube: SRT is widely used, and SBV is YouTube's own format. Your own website with an HTML5 video element: WebVTT. A video editor timeline: usually SRT. Anime or stylized typography: ASS. Music player with synced lyrics: LRC, which pairs with the song file by name. Broadcast or streaming delivery: TTML or one of its profiles. Archive or transcript: SRT plus a plain text copy.
When unsure, ask the platform which formats it accepts and pick the simplest one that works. Every format that adds features is also a format that fewer tools read.
What you lose when you convert
Plain timing and text survive almost every conversion. Features do not. Going from ASS to SRT drops positioning, fonts, colours and karaoke effects. Going from WebVTT to SRT drops comments, chapters, metadata and cue settings, and FileDial keeps only bold, italic and underline tags when writing SRT. Going from SRT to anything gains nothing automatically, because SRT has no styling to carry across.
The rule that follows is simple: keep your richest file as the master, and treat every other format as an export. If you edit an export, do not assume you can convert it back without loss.
Encoding and compatibility traps
SRT has no official character encoding and has historically used Windows-1252 as well as UTF-8 and others, which causes broken accents in some players. WebVTT requires UTF-8. If you handle languages with accents or non-Latin scripts, UTF-8 is the safe choice everywhere.
Another trap is the extension. Renaming .srt to .vtt does not convert anything, and renaming .ass to .srt will leave the style lines in the file. Use a converter. FileDial also has Edit › Shift timing… and Edit › Fix numbering for repairs that apply to the text formats, so you can correct a file before or after converting it.
A short decision guide
Ask three questions. Where will it play? If it is a browser, choose WebVTT. If a general player or editor, choose SRT. Do you need styling? If yes, and the player supports it, choose ASS, otherwise accept plain text. Is it lyrics or broadcast? LRC suits lyrics, TTML suits broadcast and streaming delivery. If the answers conflict, make the richest version first, then export simpler ones with the Convert tools. Always name files by language and format, and keep the master where you can find it.
Finally, test in the real player. A file that opens in one app can fail in another because of encoding, a missing header or an unsupported feature, so play the converted file where it will actually be used before you deliver or publish it.
Private conversion
FileDial runs every tool on your Mac and never uploads a file, and all tools work with Wi-Fi off.
Questions
Which subtitle format is most compatible?
SRT. It is plain text, and nearly every player, editor and upload form can read it. Use it unless a platform asks for something else. It is plain text, so it opens in any editor, though the file's character encoding is not standardized and can vary.
What is the difference between SRT and VTT?
WebVTT is based on SRT but requires a WEBVTT header, uses full stops instead of commas in timestamps, must be UTF-8, and supports comments, chapters and cue settings. It is designed for HTML5 video. Put another way, WebVTT is SRT's stricter, web-focused relative, and the differences are small enough that conversion is quick but not interchangeable.
When do I need ASS?
When you need custom fonts, colours, positioning or karaoke effects. It is less widely supported than SRT, so use it where your player supports it. Players that handle it well show the fonts and positions you set, while simple players may ignore styles or fail to load the file.
Will converting keep my styling?
No. FileDial's tool notes say fonts, colours and positions are not carried over when converting subtitles, so keep a master copy. Timing and words carry over, but fonts, colours and positions do not, so keep a master file in the richest format you have.