YouTube only shows chapters when three rules hold: the first timestamp is 0:00, there are at least three chapters, and each is at least 10 seconds long. Jinverse Chapters checks all three, flags anything that breaks a rule, and can fix it in one click. You can also shift every timestamp at once.
It reads messy input: notes with timestamps in the middle of a line, or SRT and VTT subtitle files. When the list is right, export it as YouTube description text, WebVTT, FFmpeg metadata, Podcasting 2.0 JSON, Markdown or CSV. There's a table of chapter lengths too.
It runs in the browser. Files aren't uploaded and there's no sign-up.
When a chapter list breaks one of YouTube's rules, YouTube just doesn't show the chapters and doesn't say why. I wanted a free tool that points to the exact rule that's broken and fixes it, without uploading files or making an account.