Working with subtitles usually involves four tasks: converting them to a familiar format, adjusting timing, extracting them from a video, and putting them back into a video. This tool combines all four functions on one page. Subtitle files are parsed and converted directly in the browser, while video-related operations are handled by the built-in engine without re-encoding the video streams.
The tool supports conversion between SRT, WebVTT (VTT), and ASS. After selecting a file, the page automatically detects the input format and shows the subtitle count. Choose the output format to preview the result, then download it after confirmation. ASS styling information is removed when converting to SRT or VTT because those formats do not support the full range of ASS style descriptions. Only subtitle text and timing are retained.
Subtitle synchronization is one of the most common problems: even a half-second delay or advance can make subtitles feel wrong. You can shift all subtitles earlier or later by a fractional number of seconds. If only one section needs adjustment, such as when the first half is correct but the second half is offset, enter a start and end time and the tool will only affect subtitles within that range. The adjusted file can be downloaded automatically, and you can also continue with format conversion.
Many downloaded videos already contain subtitle tracks. Select a video and click Detect Subtitle Tracks. The page lists the available tracks and language labels such as English or Chinese. Select the track you need and export it as a standalone subtitle file. The operation copies only the subtitle data and does not modify the video stream, so it is very fast and does not affect video quality.
Merge adds subtitles as a separate track inside the video container. The video and audio streams are copied without re-encoding, making the operation fast and lossless. After the subtitles are added, compatible players can turn the subtitle track on or off. Burning subtitles directly into the picture requires rendering fonts and libass and is planned for a later stage.
Convert ASS subtitles to SRT for broader player compatibility; convert SRT to VTT for web video; fix subtitles that are out of sync with the video; extract a specific language track from a multi-language video; or add an external subtitle file to a downloaded video without subtitles. All processing takes place on your own device.
Subtitle parsing, conversion, and timing adjustment are performed completely in the browser without network requests. Video-related extraction and subtitle muxing are also performed locally. When the page is closed or refreshed, the file references are released. Neither subtitle files nor videos are uploaded or stored on the server.
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