Does this really run without uploading my video?

Yes. WebCodecs decodes the input MP4 frame by frame in the browser, paints subtitles over each frame on a canvas, and re-encodes with the browser native H.264 encoder. Nothing is sent anywhere.

Which browsers are supported?

Captionly needs WebCodecs and WebAssembly. That covers modern Chrome, Edge, Safari (16.4+) and Firefox on most devices.

How fast is the render?

Typical 60-second 1080p clips render in 5–20 seconds on modern laptops. The bottleneck is your device's hardware encoder, not a server queue.

Will the output MP4 look identical to the live preview?

Yes. The burn-in renderer uses the same caption styling engine as the preview, frame by frame.

Can I keep the original audio?

Yes — the original audio track is muxed into the output MP4 unchanged, so the burned-in captions stay in sync.

Is there a watermark on the burned-in video?

No. The output is your video plus your captions, nothing else.

"Hello, world!"

"Amazing video!"

"Subscribe now!"

"Watch this..."

"Let's go!"

WebCodecs · No upload · No watermark

Burn subtitles into video in your browser

Drop your video and Captionly transcribes it with AI, lets you style the captions, then burns them directly into a finished MP4 — all without a server. No FFmpeg setup, no upload, no watermark, no signup.

Burning subtitles into a video used to mean installing FFmpeg, learning its flags, and waiting for an encode. Captionly does it in your browser: WebCodecs handles the H.264 encode locally, Whisper handles the transcription, and you get a finished MP4 you can post anywhere — TikTok, Reels, Shorts, LinkedIn — with the captions baked in. No service to log into, no quota to hit, and your raw footage doesn't leave your laptop.

Drop your video here

or click to browse your files

Supports MP4, MOV, AVI, WebM (max 500MB)

100% freeno signupno watermark50+ languagesSRT · VTT · TXTprivate by defaultAI-powerededit on the flyTikTok-readypodcast-readycreator-loved100% freeno signupno watermark50+ languagesSRT · VTT · TXTprivate by defaultAI-powerededit on the flyTikTok-readypodcast-readycreator-loved

✦ In-browser subtitle burner — no FFmpeg required

In-browser subtitle burner — no FFmpeg required

A real burn-in pipeline that runs locally and ships an MP4 ready to upload.

WebCodecs MP4 encode

Captionly uses the browser native H.264 encoder to render a finished MP4 — no WASM transcode, no slow path.

12 caption styles + full controls

Neon Pop, Karaoke, Bounce, Box Highlight, Pill, Outline and more — plus fine-grained controls for font, weight, anchor, padding and active-word colour.

Frame-accurate timing

Whisper produces word-level timing; the burn-in honours it frame-by-frame. Karaoke and per-word styles look exactly right.

No watermark, no signup

Free forever. No Captionly logo, no email gate, no daily quota. Render as many videos as you need.

Local — your video stays private

Captionly never uploads your video. Everything happens in the tab. No server, no third-party API.

Cancellable progress

Tweaked something? Cancel a render mid-flight, change a style, render again. No waiting for a stuck job in a queue.

✦ Showcase

Real videos.
Real captions.

See how creators of every kind are using Captionly. Drag to browse, click to play.

Cooking creator with neon style subtitles

EN0:42

Neon Pop

thischangedmylife

EN1:18

Box Highlight

andthat'swhenIquit

EN0:21

Gradient Wave

onemorerep!

EN2:04

Karaoke

Tokyoatgoldenhour

EN0:56

Bounce

bestadviceever

ES0:33

Outline

novasacreer

EN0:28

Shadow Pop

let'sgo!victory

EN1:45

Underline

watchthistrick

EN0:52

Glitch

thisisinsane

EN0:38

Minimal

feelthebeat

EN0:19

Rainbow

hitthatmove

EN0:47

Pill

waitforit

✦ FAQ

Burning subtitles — what to expect

Honest answers about how the in-browser burn-in pipeline works.

Related tools

Free · Local · No watermark

Burn the captions in your browser

Drop a video, style the captions, hit export. A finished MP4 with subtitles baked in — no FFmpeg, no upload, no watermark.

Burn subtitles now