Subtitle Soft-Embed Tool
Add toggleable subtitle tracks inside a video container. Video and audio are copied, not re-encoded, so it's much faster than burning in. Pick MP4 for broad compatibility or MKV to keep subtitle styling.
- In your browser
- Files never uploaded
- Free
Frequently asked questions
How is this different from the Burn-In tool?
Burn-in renders subtitles into video pixels, so they are always visible and cannot be turned off. Soft-embed adds subtitles as separate, toggleable tracks inside the container. Use burn-in for a finished video that must display captions everywhere; use soft-embed for multi-language options or editable text tracks.
Should I choose MP4 or MKV?
MP4 plays almost everywhere, but its mov_text subtitles are plain text. MKV keeps text subtitle tracks with their styling. Choose MP4 for compatibility and MKV for styled subtitles.
Will the new subtitle track be the default in the downloaded file?
Yes. The track you mark Default, or the first added track if none is marked, receives the container default flag. Some players may still prioritize existing source tracks or require viewers to turn captions on manually.
Why does my MP4 lose subtitle styling like font size or color?
MP4 uses the plain-text mov_text subtitle codec, which cannot carry font, color, position, or other styling. Choose MKV to keep styled subtitle tracks, or use Burn-In to render them into the video pixels.
Does my video get uploaded to a server?
No. FFmpeg reads the video from your local file handle, and subtitle parsing plus the selected mux run entirely in your browser. Nothing leaves the page.
How many subtitle tracks can I add?
You can add as many as you want. Each track has its own language code, display title, and default setting. Some players display only the first few tracks, but every selected track remains in the file.
Will the existing subtitle tracks in my video be kept?
No. By default, existing subtitle tracks are removed and replaced with the tracks you add. Turn on Keep existing subtitle tracks when you need to preserve them alongside the new tracks.
Which subtitle formats can I drop in?
SRT, VTT, ASS, SSA, SMI, TTML, DFXP, SBV, LRC, MicroDVD, and SubViewer are supported. MP4 uses plain-text mov_text; MKV keeps text subtitle formats and their styling. For ASS karaoke or transform effects, use Burn-In.
My player will not show the subtitles — what do I do?
Turn subtitles on in the player caption menu. For MP4, confirm that your player supports mov_text. Choose MKV when you need styled tracks, or use Burn-In to render captions directly into the pixels.