Optimize MP4s for HTML5 web embedding with smaller file sizes. Every conversion runs locally on your Mac — your MP4 files are never uploaded.
macOS 14 or later · Apple silicon · Free to try
MP4 is the universal video format that plays on virtually every device. WEBM is an open video format built for the web. Optimize MP4s for HTML5 web embedding with smaller file sizes.
PrivateRemix handles the MP4-to-WEBM conversion in a couple of clicks, with the result saved right next to your original file.
Unlike free online converters, PrivateRemix has no server. Your MP4 files stay on your Mac — no upload, no cloud, no account.
Drag a MP4 file into PrivateRemix, or pick one from your Mac.
Select WEBM from the formats PrivateRemix offers for your file.
The new WEBM appears next to the original. Nothing leaves your Mac.
The change is minimal. Both formats are compressed, and PrivateRemix converts at a high quality setting so there is no visible or audible drop for everyday use.
For sharing and playback, yes — MP4 is supported by nearly every phone, TV, browser and editor, which is why it's the safe default.
WEBM is designed for browsers and isn't natively supported by QuickTime or many editors. Converting to MP4 makes it play in almost any player.
No. PrivateRemix runs entirely on your Mac using its own processor. Your MP4 files never leave the device — there is no server to upload to, and it works fully offline.
Yes. Drop in a batch of MP4 files and PrivateRemix converts them all locally, saving each new WEBM next to its original.
Free to try. macOS 14 or later, Apple silicon.