Burn Subtitles Into a Video

What burning in actually does

A video file holds pictures and sound. Ordinary subtitles sit beside them as text, and the player draws that text over the image at playback time. Burning in moves the drawing step earlier: each frame is decoded, the line for that moment is painted onto it in the font, colour and position you chose, and the frame is encoded again into a new file. From then on the words are pixels, exactly like a logo or a lower third, so every app, TV, projector and messaging service shows them whether or not it understands subtitle files.

That permanence is the whole point, and it is also the cost. Nobody can turn the text off, swap it for another language or correct a typo without rendering again from the original. Keep the source video and an exported SRT next to the burned copy, and a correction next month takes minutes instead of a fresh transcription. The file-level background is in embedded versus sidecar subtitles.

Burning subtitles in, step by step

1. Open the editor and pick the video from your computer. MP4, MOV, M4V, WebM and MKV files open; AVI files do not, so convert those first with a tool such as HandBrake.
2. Get the lines in: keep "Write the subtitles automatically with AI" switched on, use Import SRT / VTT for a file you already have, or pause at the right moment, press Enter and type.
3. Play the video through once with the line list beside it. Correct wording in the list and drag a line's edges on the timeline wherever a caption arrives early or lingers.
4. In the Style tab choose a preset, then adjust font, size, outline or box and position. Turn on "Show safe area" if the video will be watched inside an app with its own buttons.
5. Click Render video. The "Ready to render" summary shows what will be produced; start it and keep the tab open until Download video appears.
6. Save the MP4, which carries the source name with -subtitled added, and press Export SRT too if you may need to edit or reuse the text later.

Soft or burned: decide before you render

Burned and soft subtitles answer different questions, and plenty of projects end up wanting both.

Shows on every player

Burned: yes, it is part of the image. Soft: only where the player or platform reads the subtitle file.

Viewer can hide it

Burned: no. Soft: yes, with the CC button or the player menu.

Languages per video

Burned: one per rendered copy. Soft: as many files as you care to upload.

Look and position

Burned: exactly what you saw in the preview. Soft: chosen by the player, often plain white text.

Fixing a mistake

Burned: edit the line and render again. Soft: edit the text file and replace it.

Search and indexing

Burned: platforms can't read pixels as words. Soft: YouTube and similar sites can index the file.

A workable rule: burn in when you don't control the player, such as social feeds, chat apps, screens in public spaces, or a client who will forward the file around. Use soft subtitles when the platform accepts them and viewers gain something from choice. If a soft file is all you need, the AI subtitle generator hands you an SRT or VTT without rendering any video.

What the render does to your file

The download is a new MP4, not your original with something bolted on. It keeps the source's resolution, frame rate and orientation, so a 4K vertical clip comes back as a 4K vertical clip, with no downscaling and no watermark. The picture is compressed as H.264 whenever your browser can encode that size, and falls back to HEVC, VP9 or AV1 when it can't. The soundtrack is copied across untouched if MP4 can carry it; otherwise it is converted to AAC or Opus.

Every re-encode gives up a little, and this one is no exception, so the editor counters it by picking a bitrate that normally sits above the source's own. Most viewers can't tell the subtitled copy from the original, but if you are delivering to a broadcaster or archiving a master, keep the untouched file as well. HDR footage is the one case with a visible change: it comes out as SDR, and the editor warns you before you start. Burning without losing quality goes further into bitrate and choosing the right source.

Where rendering happens, and its limits

Encoding runs inside your browser through its built-in video encoder (WebCodecs), on your own processor and graphics hardware. That is why there is no upload wait and no queue, and also why a few limits depend on your machine rather than on mydubly:

• Browser: Chrome or Edge 94 or later, Safari 16.4 or later, or Firefox 130 or later, on a desktop or laptop. Phones and tablets can edit and export subtitle files, but don't count on them to render.
• Space: long files stream to the browser's private storage on disk where that is available; otherwise the whole job has to fit in memory. If the device runs short, the render is refused, and there is no server to hand it to instead.
• Time: it depends on length, resolution and hardware, and the tab has to stay open until the download is offered.
• Connection: the page and its fonts load from the internet, so you need to be online to begin.

If the footage already has old subtitles in the picture, "Hide subtitles already in the video" blurs a horizontal band so your new lines sit on a softened strip. It blurs rather than erases, which hiding burned-in subtitles explains properly.

Get the text right before it becomes permanent

A burned-in mistake ships with every copy, so the review pass matters more here than it does for a subtitle file. The editor flags lines that overlap, stay up for under 0.8 seconds, run faster than about 21 characters per second, or stretch past 42 characters (those wrap automatically). Clear the warnings that matter, then watch once at normal speed with the sound on.

If AI wrote the draft, your browser sent only the audio for transcription with Whisper while the picture stayed on your computer, and the job cost 1 credit per minute of video, with a minimum of 5 credits. Treat the result as a first pass: check names, numbers and product terms against what was actually said, and use the review routine for auto-generated subtitles if the video is long.

Three burns, start to finish

Going the other way, from one spoken language to subtitles in another, is covered on burning translated subtitles.

About the subtitle editor on this page

Opens

MP4, MOV, M4V, WebM, MKV videos your browser can decode

Subtitles from

AI (from the speech, optionally translated into one of 21 languages), an SRT or VTT file, or typing them in

You download

An MP4 with the subtitles drawn into the picture at the original resolution and frame rate, plus SRT and VTT files

Cost

Editing, styling, rendering and SRT/VTT export are free, with no account and no watermark. AI subtitles cost 1 credit per minute (5-credit minimum per video); signing in with Google gives 100 free credits and accounts get 10 free credits a day

Privacy

The video never leaves your device and is rendered in your browser. Only for AI subtitles is the audio sent, over HTTPS, and it is deleted within 30 minutes of delivery

Rendering needs

Chrome or Edge 94+, Safari 16.4+, or Firefox 130+ on a computer. Editing and SRT/VTT export work in any current browser