Convert WebM to MP4
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WebM is great on the web — it’s what a lot of screen recorders, browser-based tools, and streaming sites export by default — but it’s a poor fit for video editors, older phones, or anywhere MP4 is the expected standard. This tool re-encodes your WebM into MP4 (H.264/AAC) using your browser’s native codec support, which keeps things fast.
Because it leans on WebCodecs, the encode step runs directly on your device’s hardware, and the file itself never touches a server — it goes from your disk, through the browser tab, and back to your downloads folder.
Also useful: Convert MP4 to WebM · Convert MOV to MP4
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Frequently asked questions
Why is my WebM file not playing on my phone or in my editor?
Many editing apps and older devices only expect MP4 with H.264 video, and don’t recognize WebM’s VP8/VP9 codecs at all. Converting to MP4 fixes that instantly.
Does this tool send my video to a server?
No — decoding and encoding both happen locally using the WebCodecs API. Your file stays on your device the entire time.
What are the size, length, and browser requirements?
Up to 300MB on desktop (100MB on mobile), and up to 30 minutes long on desktop (10 on mobile), since this re-encodes video. You’ll need a current Chrome, Edge, Firefox, or Safari for WebCodecs support.