Why this tool is useful
Recover an embedded caption track for editing, accessibility review or translation without sending a large private video to a conversion server.
Local File Tools · runs locally
Private MP4 Subtitle Track Extractor
Extract embedded tx3g or WebVTT subtitle samples from an owned MP4 or MOV file and save a normalized SRT without uploading the video.
Ready. Your working data stays in this browser.
Files stay on this device. Processing uses browser APIs only; nothing is uploaded to YTSave, the media API or a proxy.
How it works
The browser reads a bounded MP4 moov box, maps the subtitle sample tables to their byte ranges and loads only the allowed tx3g or wvtt samples. It then normalizes cue timing and text into an SRT Blob in this tab.
Practical example
Select an MP4 containing a tx3g caption track, verify the detected codec and cue count, then download the extracted UTF-8 SRT file.
Validation
The calculation is deterministic and explains validation errors instead of silently changing invalid input.
Privacy boundary
Input and output remain in this tab. Copy and download happen through browser APIs without a server upload.
Result passport
Every run reports its tool mode, timestamp and input/output size so transformed data can be audited.