Closed Caption File Format Guide for YouTube
Youtube (Without Integration)
YouTube recommends Scenarist (.scc) format. Rev also recommends TTML or WebVTT; any of these three options provides some control over appearance of your captions on the YouTube platform.
Compatible formats:
SubRip (.srt)
WebVTT (.vtt)
DFXP/TTML (.dxfp)
Scenarist (.scc)
SAMI (.sami)