Pair subtitle cues by time overlap, preserve the primary timeline and flag missing or ambiguous matches before exporting.
Your input
Outputs are cleared when the input changes.
Result
Enter your data or use the example, then run the tool.
Worked example
The matching Hello/你好 and World/世界 samples produce two cues with the primary language above the secondary. One secondary cue claimed by two primary cues is ambiguous and blocks subtitle download.
Method
On the primary timeline, consider overlapping secondary cues meeting the minimum ratio, then select the unique largest overlap in milliseconds. Ties or a secondary cue claimed by multiple primaries are ambiguous. Any missing/ambiguous/unused cue blocks subtitle export; edit the inputs and run again. No translation is performed.
Limits
Each input: at most 2 MiB UTF-8 and 10000 cues, output 4 MiB, timeline seven days. Plain cues only: WebVTT settings/NOTE/STYLE/REGION/timestamp maps and advanced markup are rejected. Unicode and basic i/b/u are preserved; no speech recognition. Large bounded operations may briefly occupy the main thread. At most 100000 actual overlap pairs; reports and preview can be downloaded as JSON, not as a complete subtitle when unresolved.
Your inputs stay on this device. Only optional, consented page visits are measured. Input values, files, filenames and processing logs are not sent to Analytics.
When switching languages, text, settings and selected files are temporarily kept on this device. Transfers are removed after restoring; interrupted transfers are cleaned up on a later visit. Inputs and files are never uploaded.