If the file is for a mainstream or catalogued video, these community-driven sites are the most reliable sources:
: Allows you to upload a video or use a link to generate and then download a transcript as an SRT file. Advanced Retrieval Download OKSN 278 srt
: Focuses primarily on television shows and series if the ID refers to an episodic release. How to Extract SRT Files Directly If the file is for a mainstream or
: A free web service where you can paste the video URL to download available subtitles in SRT format. Download OKSN 278 srt