Have the script but no subtitles? Paste the text, one line per subtitle, and get a timed SRT. Nothing is uploaded.
A .srt where each line is one subtitle, back to back from 0:00. Each one lasts as long as it takes to read at your pace, and at least one second.
Clipped Cloud
Still typing subtitles by hand? Clipped Cloud captions your clips for you.
From the number of words. At the default 2.5 words a second (about normal speech), a 10 word line lasts 4 seconds. Raise it for fast talkers.
It gives an even first pass, not a sync to the audio. Fix single lines in the SRT editor, or move everything with the timing adjuster.
One short line per subtitle. About 40 characters, or 5 to 8 words, reads well on a phone. Empty lines are skipped.
No. Nothing is uploaded. The file is read and converted by your browser, on your device. It even works offline once the page has loaded.
On iPhone? Get the Clipped app, free. It cuts clips for you.