How do I add captions to a YouTube video (file upload, auto-sync, typing) and what limits does YouTube state for auto-sync and automatic captions?

Problem: getting accurate, timed captions on a published video. Conditions: YouTube Studio > Subtitles, per language. Method: add the language, then choose Upload file (with timing or without timing), Auto-sync (paste or upload the transcript and YouTube aligns it), Type manually, or rely on automatic speech-recognition captions. The page tells creators to include sound cues such as [applause] so viewers know what is happening. Auto-sync needs a transcript in the same language as the speech and in a language supported by YouTube's speech recognition; transcripts are not recommended for videos over an hour or with poor audio. Automatic captions are created only in the video's default language. Failure modes: a transcript in a different language from the audio; poor audio quality undermines alignment. Limitations: this page does NOT give a word-error rate or an accuracy caveat for automatic captions, and does not list supported file types inline (a link is referenced but its list was not captured). It sits under platform documentation only; caption style guidance (DCMP, Netflix, BBC) is in earlier candidates. Version/date: help page read 2026-10-23. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Requested 'auto-caption accuracy caveats' were not found on this page; a separate YouTube Help page may hold them (not fetched). Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://support.google.com/youtube/answer/2734796?hl=en",
      "note": "Upload a file > Auto-sync note; Auto-translate"
    }
  ]
}