Why this tool is useful
Use Private Subtitle Timeline Preview when you need to inspect cue count, duration, overlaps and a bounded cue-text preview without rendering media while keeping the source file on your device.
Local File Tools · runs locally
Private Subtitle Timeline Preview
inspect cue count, duration, overlaps and a bounded cue-text preview without rendering media entirely in your browser without uploading the selected file.
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 validates the declared file type and 10 MiB limit, then runs the subtitle preview operation locally. No downloader job or proxy is involved.
Practical example
Choose a supported file, review the locally produced previewed cues, and download a result only when this operation creates one.
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.