Is my WebP uploaded to a server?

No. Frames are decoded in your browser with WebCodecs and encoded with ffmpeg compiled to WebAssembly. The file never leaves your device — only the ffmpeg engine code is fetched once from a CDN and then cached.

Why does it need WebCodecs / which browsers work?

ffmpeg's current core cannot decode animated WebP, so the frames are decoded with the browser's native WebCodecs ImageDecoder. That is supported in Chrome, Edge, and Firefox. Safari does not expose it yet, so use one of those browsers.

Does it keep the original animation speed?

Yes, if you choose Preserve timing — each frame keeps its own duration via ffmpeg's concat demuxer. You can instead pick a fixed frame rate to force a constant fps.

What quality setting should I use?

The CRF controls H.264 quality: lower is better and larger. 18–23 looks visually lossless to near-lossless; 24–28 is a good size/quality balance for web.

Why is the first conversion slower?

The first run downloads and initialises the ffmpeg core (about 10 MB gzipped). After that it is cached, so later conversions start immediately.

WebP to MP4 Converter

Convert an animated WebP to an H.264 MP4 entirely in your browser — preserve the original timing or set a fixed frame rate. Your file never leaves your device.

Converted entirely in your browser — the WebP is never uploaded. Frames are decoded with WebCodecs and encoded with ffmpeg.wasm; only the ffmpeg engine is fetched once from a CDN and cached.

WebP file

Pick an animated (or static) WebP. Read locally — nothing uploaded.

Output options

Timing

Quality — CRF (23, lower = better)

Max width

About

About WebP to MP4 Converter

Animated WebP is compact, but many editors, messengers, and social platforms want an MP4. This tool converts an animated (or static) WebP into an H.264 MP4 without uploading anything. Because ffmpeg's WebAssembly core cannot yet decode animated WebP, the frames are first decoded in your browser with the native WebCodecs ImageDecoder, then encoded to MP4 by ffmpeg.wasm — so the file stays on your device the whole time.

You can preserve each frame's original duration (variable timing) or force a constant frame rate, set the H.264 quality (CRF), and optionally downscale the width. The output uses yuv420p pixel format with the moov atom moved to the front (faststart), so it plays in browsers, QuickTime, and mobile players. A live preview plays the result before you download it.

Frame decoding uses the WebCodecs ImageDecoder API, which is available in Chromium-based browsers (Chrome, Edge) and Firefox. Safari does not yet expose it, so use one of those browsers there. The first conversion downloads the ffmpeg engine (about 10 MB gzipped) and caches it for next time.

How to use WebP to MP4 Converter

Choose a WebP
Pick an animated (or static) WebP. It is read locally in your browser and never uploaded.
Set the output
Preserve the original frame timing or pick a fixed fps, choose the quality (CRF), and optionally set a maximum width.
Convert
Click Convert. Frames are decoded in your browser, then encoded to MP4 by ffmpeg (downloaded once, then cached).
Preview and download
Play the MP4 preview, check the size, and download it.

Frequently asked questions

MP4 to WebP Converter

Convert an MP4 video to an animated WebP entirely in your browser — powered by ffmpeg.wasm. Tune fps, width, quality, loop, and trim. Your video never leaves your device; nothing is uploaded.

How it works

Why decode in the browser?

Timing & quality

Browser support

Privacy