Private subtitle workflow in your browser
Add subtitles to a video online
Add SRT, WebVTT, ASS, or SSA captions to a video with a live preview. Keep subtitles switchable as a text track, or burn them into the picture for playback on almost any player. The video and subtitle file are processed locally in your browser.
Supported video and subtitle formats
The file picker accepts common camera, phone, screen-recording, and editing-app exports. Actual video decoding depends on the codecs available in your browser.
Video: MP4 / M4V
Best compatibility
The recommended input for phones, social platforms, and most browsers.
Video: MOV / WebM
Camera and web exports
Useful for Apple devices, screen recordings, and browser-based projects.
Video: MKV / AVI
Local media files
Accepted up to 2 GB when your browser can decode the streams inside the container.
Subtitles: SRT / VTT
Simple timed text
SRT is widely supported; WebVTT is designed for HTML5 video and web players.
Subtitles: ASS / SSA
Styled subtitle files
Text and timing are imported locally; styling is applied using the editor settings for burn-in.
How to add subtitles to a video
Prepare a captioned video in four straightforward steps.
- 01
Add your video
Drop a video into the first panel, or choose it from your device.
- 02
Add a subtitle file
Choose an SRT, VTT, ASS, or SSA file. The tool validates and counts its timed cues.
- 03
Preview and choose a mode
Play or seek the video, check the matching cue, then choose soft subtitles or burn-in.
- 04
Style, export, and download
Tune the burn-in style when needed, export locally, and download the finished file.
Common subtitle use cases
A subtitle track is useful well beyond simply translating a finished film.
Social media captions
Burn captions into short clips so they remain visible when a platform or viewer has captions turned off.
Accessible video
Keep a selectable subtitle track for viewers who need captions, different languages, or custom playback controls.
Course and meeting recordings
Add prepared notes, speaker dialogue, or translated captions to lessons, demos, and recorded calls.
Localization and review
Preview a translated SRT or VTT with the original video before delivering it to an editor or client.
How are my video and subtitles handled?
The selected files are read as browser File objects. MediaBunny and WebCodecs decode, compose, and encode them on this device; the source and result are not uploaded to MediaKit servers. Remove the files or close this tab when finished to release browser memory. A modern Chromium-based browser with WebCodecs is recommended for the best export performance.
FAQ
Frequently asked questions
Which subtitle formats can I import?
The parser accepts SRT, WebVTT (VTT), Advanced SubStation Alpha (ASS), and SSA files. Timing and text are normalized into cues for preview and export.
What is the difference between soft subtitles and burn-in?
Soft subtitles remain a selectable text track that viewers can turn on or off. Burned subtitles become pixels in every video frame, which makes them more compatible but no longer editable as a track.
Will ASS styles be preserved?
ASS and SSA text and timing are imported. For burn-in, use the page controls to choose the text color, background, size, position, and weight; SRT/VTT exports contain timed text rather than visual styling.
Will the original audio be kept?
Yes. The export keeps the primary audio track when the selected output container and browser support it.
Why can an MKV or AVI file fail?
A container may hold codecs that your browser cannot decode. MP4 with H.264 video is the most reliable input; converting the source first can help with unusual codecs.
Can I add subtitles without uploading my video?
Yes. This page is designed for local browser processing. No server upload is required for subtitle parsing, preview, or export.
Can the tool create subtitles from speech?
No. It adds existing timed subtitle files. Use a speech-to-text workflow first when your video does not already have captions.
Related video tools and subtitle guides
Subtitle timeline editor
Fine-tune cue text and timecodes before adding the track to your video.
Open tool or guideSubtitle format converter
Convert SRT, VTT, ASS, and SSA while keeping the timing available for editing.
Open tool or guideExtract subtitles from video
Read an embedded text subtitle track and download it as SRT or WebVTT.
Open tool or guideHow to add subtitles to a video
Learn when to use soft subtitles, burn-in captions, and web-friendly formats.
Open tool or guide