An STR file is a recording file created by YouTube for a livestream that was hosted by user’s streaming event. The file is saved automatically by Youtube at its backend once the live streaming is over. A live streaming video can be broadcasted to multiple channels so as audience can interact with publisher via comments. These SRT files are accessible using YouTube livestream API that provides access to the YouTube’s servers.
STR File Format
YouTube saves STR files to server in binary file format. The internal file structure details of STR files is not available publicly though.