认出它原本是什么编码，把读错的字换回去。字幕的序号、时间轴一个字都不动。
Subtitles that open as a wall of nonsense are almost always read with the wrong encoding. Drop the file in, and it works out which encoding the file was really written in and puts the misread characters back.
Uploaded files are re-decoded from the original bytes, so nothing is lost: if the file turns out to be GBK, it says so, and if your player is the one misreading it, saving a copy as "UTF-8 with BOM" usually settles it. Pasted text is no longer the original bytes, so much less can be recovered; if it already contains replacement characters, that is unrecoverable and the tool says so plainly instead of pretending otherwise. Line numbers and timecodes are never touched, and ASS style tags are left exactly as they were.
Anyone who downloaded subtitles that open as gibberish, sees boxes instead of Chinese in the player, or was handed a file with an unknown encoding.