[simsla]

At least for English, those "fansubs" aren't typically burnt into the movie*, but ride along in the video container (MP4/MKV) as subtitle streams. They can typically be extracted as SRT files (plain text with sentence level timestamps).

*Although it used to be more common for AVI files in the olden days.

[Maken]

SRT is ancient. Nowadays everyone uses ASS subtitles which can be randomly styled.

[simsla]

In general? In the past I've known ASS to be used a lot for things like anime, but less for live action shows.

[Maken]

I have also found them inside mkvs as the subtitle track. I think SRT was the default because most content was ripped from DVD/BD, but now most of the content is from streaming sources and you need to convert the subtitles anyway.

[conradev]

WebVTT (a SubRip successor) is probably more widely used than ASS

[Maken]

By legit providers, probably.

[ethbr1]

flashbacks of trying to track down subs sync’d to a specific release