Subtitle Converter

If you are adding captions to a video on a website, WebVTT is usually what you need. The HTML video element loads captions through a track element, and the HTML standard expects those tracks to be WebVTT. A plain SRT file will not show up in most browsers even though it looks almost identical in a text editor.

The differences are small but strict. A VTT file must begin with the word WEBVTT on its first line. Timestamps use a period before the milliseconds, as in 00:01:02.500, where SRT uses a comma. Cue numbers are optional, and a cue can carry settings for position, alignment and line, plus voice and class tags that a page's CSS can style. Converting SRT to VTT adds the header and changes the separators; converting the other way removes everything SRT cannot express.

SRT remains the most widely understood file outside the browser. Desktop players, smart TVs, editing software and most streaming uploads read it, which makes it the right target when you do not know where the file will end up. The format comes from the old SubRip program and has never had a formal specification, so stick to the plain form of numbered cues, times and text if a device is fussy.

Converting never touches the video. Subtitles here stay as a separate file that the player lays over the picture, which keeps them switchable and easy to correct later. Captions that are burned into the image, sometimes called hardcoded or open captions, are part of the video frames themselves; they cannot be extracted or converted as text, only read again with speech or text recognition.

Most sync problems fall into two kinds. If every line is off by the same amount from start to end, the subtitles were made for a version of the video with a different intro or a trimmed opening. Shift timing moves all cues by the number of seconds you enter, with decimals allowed, so a value of 1.5 delays everything by a second and a half, and a negative value pulls everything earlier.

If the offset grows as the film goes on, the subtitles were timed against a different frame rate. Films are shot at 24 or 23.976 frames per second, while European PAL broadcasts and many old DVDs run the same film at 25, which plays it about four percent faster. Set Original frame rate to the rate the subtitles were made for and Target frame rate to the rate of your video, and every timestamp is rescaled to match. The same settings convert frame-based MicroDVD SUB files, which count frames instead of seconds. If you are unsure which rate a video uses, the file details in most players or editors list it, and the subtitle rate is usually the other common value.

Seconds per line applies when the source has no end times, as in LRC lyric files and some plain-text inputs: each line stays on screen for the time you set. Input encoding is set to auto-detect, which reads UTF-8 and the common Windows code pages. If accented letters, Cyrillic or Arabic text still come out as symbols, pick the encoding the file was saved in, such as Windows-1251 for Russian or Windows-1256 for Arabic. The output is saved as UTF-8, which is what YouTube and current players expect.

Remove formatting tags strips bold, italic, color and font tags along with ASS override codes, leaving clean text. It is useful before handing captions to a translator or a service that rejects markup. To trim the video itself so it matches the captions, use the Trim Video tool; to change the video file's format, the video converter keeps the timeline intact.

File names matter as much as the format for players that pick up subtitles on their own. Give the subtitle file the same base name as the video, and many players, including VLC and common media servers, load it without being asked. When you have several languages, a language code between the name and the extension, as in movie.en.srt and movie.es.srt, lets those players label the tracks. Keep a copy of the original file before you shift or rescale anything, so you can start again from a clean version if a correction goes too far.