Converting SRT and VTT should preserve the text and boundaries of each cue. An offset shifts the start and end times by the same number of seconds. After exporting, check the file in a player: correct syntax does not confirm that the words match the speech.
Short file for testing
Download the sample SRT: the first cue starts at 00:00:01,000 and ends at 00:00:03,500, the second runs from 00:00:04,000 to 00:00:07,000. This is an artificial example without a source video. The VTT of the same example preserves the same times and uses the corresponding format entry.
Open the chapter and subtitle editor, select SRT / VTT, and upload the file. Specify an offset of 1,5 seconds: the first cue should become 00:00:02,500–00:00:05,000, and the second 00:00:05,500–00:00:08,500. Check both boundaries, then download the desired format.
Supported subset
The tool works with plain cue text. Tags and internal timestamps are rejected: shifting only the outer boundaries would leave an internal timestamp in its old place. WebVTT also describes styles, regions, and placement settings; this export does not carry them over.
A regular line break is allowed within a cue, but not an empty line between paragraphs: it separates the file's blocks. If an edit creates such a gap or service angle brackets, fix the text before downloading. A negative offset that pushes the start below zero also requires a change.
Checking after conversion
Re-upload the downloaded file and verify the number of cues, the start, the end, and the text. Then check the beginning, middle, and end of the actual video. If the desynchronization increases toward the end, a single offset will not solve the problem: the editing or the source duration may differ.
The editor does not recognize speech and does not obtain subtitles from someone else's video. To publish, you need a file you have the right to use. Check automatic subtitles separately for names, numbers, and negations; correct timing markup does not fix a semantic error.
If a separate public video has been prepared for this work, you can check the current view terms. Preparing chapters and subtitles is free; ordering views does not fix the video's metadata. Purchased activity does not confirm organic interest, recommendations, leads, or sales.