SRT file not working? Work through this in order
A subtitle file that refuses to load almost never fails in an interesting way. It is the filename, the folder, the encoding, a malformed timing line, or the player looking at something else entirely. Here they are in the order that finds the problem fastest.
1. The filename and the folder
Most players load a sidecar subtitle automatically only when it sits in the same folder as the video and shares its name exactly, extension aside: my-film.mp4 next to my-film.srt. The near misses are what catch people. my-film.mp4 with my-film.en.srt works in some players and not others. my-film (1).mp4 with my-film.srt does not match. A file that Windows is showing as my-film.srt may actually be my-film.srt.txt with the real extension hidden. If the automatic load is failing, open the subtitle file manually from the player's own menu. If it works that way, the file is fine and the problem was the name.
2. The timing lines
Open the file in a plain text editor and look at the first few blocks. A valid SRT timing line looks like this, and the parts are less forgiving than they look: 00:00:01,000 --> 00:00:04,120 Two digits for hours, minutes and seconds. A comma before the milliseconds, not a full stop — a full stop is WebVTT. Three digits of milliseconds. Spaces either side of the arrow, and the arrow is two hyphens and a greater-than sign. If a converter or a spreadsheet has been anywhere near this file, the comma is the thing most likely to have changed.
3. The character encoding
If the subtitles appear but the accented characters are wrong — Ã¥ instead of å, question marks instead of dashes — the file loaded fine and is being read in the wrong encoding. Re-save it as UTF-8 from any text editor. This one can also stop a file loading outright: a few players give up on a subtitle file containing bytes that are not valid in the encoding they assumed.
4. Captions that are already in the video
If the video already carries its own subtitle track, some players prefer it and quietly ignore your sidecar file. Open the player's subtitle menu and look at what is actually selected — if there are two entries, you are choosing between the embedded track and yours. The same thing happens the other way round: subtitles you cannot turn off are burned into the picture, and no subtitle setting will remove them.
5. Where you are playing it
Sidecar subtitle files are a desktop convention. Casting to a TV, playing through a streaming box, or handing the file to a phone gallery app very often means the subtitle file is simply not part of what gets sent. If the subtitles work on your computer and vanish on the television, nothing is wrong with the file — the path it travelled dropped it. Either play through software that carries subtitles across, or mux the subtitles into the video file so they travel with it.
6. The file has structure problems you cannot see
Overlapping cues, a block with a timing line and no text, timings that run backwards, a stray byte-order mark at the top, Windows line endings where the parser expects Unix ones. Any of these can make a strict player reject a file that looks fine in an editor. Pasting the file into the tool on the front page is a quick way to find out: it reports how many captions it found, how long they run, and how many overlap. If it reads 300 captions and your player shows none, the file is not the problem. If it reads 4, you have found where the file breaks.
Frequently asked questions
Why do my subtitles work in VLC but not on my TV?
Because the sidecar file never reached the TV. VLC reads the .srt sitting next to the video; most casting and streaming paths send only the video. Muxing the subtitles into the video file is the reliable fix.
My subtitles show up as strange characters. Is the file corrupt?
Almost certainly not. It was saved in one character encoding and is being read in another. Re-saving as UTF-8 fixes it, and no timings or text are lost.
Can an SRT file be too large?
Not in practice. A feature-length subtitle file is a few tens of kilobytes. If a tool is rejecting yours for size, it is much more likely rejecting it for format.
Does renaming a .txt file to .srt make it a subtitle file?
Only if the contents are already in SubRip format — numbered blocks with timing lines. Plain prose renamed to .srt has no timings in it, so there is nothing for a player to show. That text needs timing first.
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