Burn Subtitles into Video — Hardcode SRT & VTT Online

Hard subtitles that play everywhere

A separate subtitle file only works when the player or platform supports it. Many social networks, messaging apps and presentation tools ignore .srt files, and viewers often scroll with the sound off. Burning, or hardcoding, the subtitles draws the text directly into the video frames, so the captions appear on every device and every platform exactly as you styled them. The trade-off is that burned captions cannot be switched off or edited later, so keep your original video and subtitle file.

Everything happens in your browser. The video is processed with ffmpeg.wasm, a WebAssembly build of ffmpeg that runs on your own device, so private recordings and client projects are never uploaded. The first run downloads the ffmpeg engine; later runs in the same tab reuse it.

How the captions are rendered

Each subtitle cue is drawn with the browser's canvas using your system fonts, wrapped to fit 90% of the frame width, and saved as a transparent PNG. ffmpeg then overlays each image on the video only between that cue's start and end times and re-encodes the result as H.264 MP4 with AAC audio. Because the text is rendered by the browser, any script your device can display works, including Cyrillic, Arabic and CJK characters, with no font files to install.

Font size and margin are percentages of the video height, so the same settings look consistent on a vertical phone clip and a 4K landscape video. A black outline keeps white text readable over bright scenes, while the semi-transparent box gives the classic broadcast look. Use Preview first subtitle to see the style on a real frame before encoding.

Tips and limits

Re-encoding takes time and memory proportional to the video's length and resolution. Short clips at 1080p are usually fine; for long or 4K videos, resize or trim first. Up to 400 cues are supported per video, which covers typical social clips, tutorials and talks. If your subtitle timing is off, fix it in the subtitle editor or regenerate it with the auto subtitle generator before burning, since burned captions cannot be corrected afterwards.