What an SRT file has to contain

A cue is an index, a line with --> between two timestamps, the text, and a blank line. Times look like 00:00:01,000. A dot before the milliseconds is accepted. A missing arrow is reported as a broken block and that block is not timed.

Overlaps are separate from broken syntax. If cue 4 starts at 4.500 s and cue 3 ends at 5.000 s, both blocks are valid SRT and the schedule is still wrong. timing fixer trims the earlier cue to one millisecond before the next start, and it can shift every cue by a number of milliseconds you type.

Export writes captions.srt from the box. Ctrl+Enter or ⌘+Enter runs the export while the tool is focused. Open the file in a player before you publish.