Subtitle Workbench
Give a caption file a careful handoff. The local workbench keeps timing and text editable while showing what source styling and metadata will not survive.
How we build a check
This workbench processes supported inputs locally. We test calculations, file structure and generated artifacts using independent readers or known fixtures where available. The example runs the same processing path as a supplied input; it does not stand in for checking your own result.
Editorial responsibility
KitForma maintains this tool and its guides. The source notes on the tool page link to the supporting documentation. We do not claim affiliation with the referenced hardware manufacturers or platforms. Review date: 2026-10-19.
Limits and updates
UTF-8 input up to 2 MiB and 5,000 cues; times below 100 hours. SRT, WebVTT, ASS/SSA dialogue and simple TTML media-clock/seconds/milliseconds input. TTML ancestor/span timing, frame/tick timing, ASS drawings and segmented VTT timestamp maps are rejected. No broadcast SCC/EBU-STL, OCR, transcription, translation, waveform, burn-in or style-preserving export. Optional local media up to 512 MiB uses browser codecs. If a specification changes or a result appears incorrect, send the relevant source URL and a non-sensitive reproduction to kitforma@outlook.com.
Open-source components
The tools use self-hosted open-source components appropriate to each format, including PDF.js, pdf-lib, fflate, SheetJS, MediaInfo by MediaArea.net SARL and others. Component versions and licenses. MediaInfo license · fflate license.