SyncMySubsConvert SUB to VTT
Convert a .sub subtitle to WebVTT .vtt for HTML5 video and the web. The .sub extension covers two very different formats, MicroDVD and SubViewer, and this tool detects which you have. MicroDVD stores frame numbers, so you can set the frame rate to get the timing exactly right. It runs in your browser; nothing is uploaded.
This is a frame-based MicroDVD file, so its timing depends on the video's frame rate. If the file declares its own rate that is used; otherwise pick the rate that matches your video.
Two SUB formats, one output
Files ending in .sub come in two flavours. MicroDVD stores each line as frame numbers like {25}{50}, which only become real times once you know the video's frame rate. SubViewer stores clock times directly. This tool inspects the file and reads whichever it is.
For a MicroDVD file, pick the frame rate that matches your video (or let an embedded rate win) so the timing lands correctly; for SubViewer no rate is needed. Either way, the output is a valid WebVTT file with a WEBVTT header and standard cue timing, ready for an HTML5 <video>.
FAQ
MicroDVD or SubViewer, how does it know?
It inspects the content. Curly-brace frame markers like {25}{50} mean MicroDVD; a header and HH:MM:SS timing lines mean SubViewer. The right parser is chosen automatically.
Why does the frame rate matter?
MicroDVD stores frames, not time, so a frame rate is needed to convert them. If it's wrong, the subtitles drift. Set it to your video's rate (commonly 23.976, 25, or 29.97). SubViewer files already hold clock times, so no rate is needed.
Is my file uploaded?
No. The conversion runs in your browser. Your file never leaves your device and no server is involved.