Convert WebM to MP4
WebM plays in browsers and often nowhere else.
It happens on your device. Nothing is uploaded — including video.
What changes when you convert WebM to MP4
- MP4 is lossy. The quality control is a real trade, not a placebo — Smallest, Balanced and Best produce genuinely different files.
How to do it
- Drop your WebM file above, or click to browse. A whole folder works too.
- MP4 is already selected. Change it on any row if you want something else.
- Pick a quality — Smallest, Balanced or Best. Balanced is a good default.
- Press Convert, then Save. Nothing left your machine.
Questions
- Is my WebM file uploaded anywhere?
- No. The conversion runs inside this browser tab using WebAssembly. There is no server involved, which is why there is no file-size cap, no queue and no account. The counter in the header measures bytes this page sends, and it stays at zero.
- Is there a file size limit?
- No imposed limit, but a real one: a browser tab has roughly 1.8 GB of working memory. Onhand estimates before it starts and tells you if a file is too large, rather than failing halfway through.
- Does it work offline?
- After one visit, yes. The page and the codecs it has used are cached, and the badge appears only when the codecs for your chosen formats are genuinely available offline — not merely because something is installed.
- Can I convert several files at once?
- Yes. Drop a folder, or select many files. Each row gets its own target format, or you can set them all at once, and everything downloads as a single zip.