Convert WMV to MP4

Yes. FFmpeg runs entirely in your browser via WebAssembly. Your files are never uploaded, streamed, or seen by any server — including ours.

Around 2 GB, and it's a browser limit rather than ours. WebAssembly can only address so much memory, so the whole job has to fit in the tab. Lightweight operations that copy streams instead of re-encoding (trimming, remuxing, stripping the audio track) work on files right up near that ceiling, because the file is read in place instead of being copied into memory. Full re-encodes need room for the input, the output, and working memory at once, so their practical ceiling is lower — lower still on phones. For anything bigger, the exact same command runs with no size limit on the Rendi API.

Yes. It's a web page, so it opens in Safari or Chrome on a phone the same way it does on a laptop: nothing to install, and your files still never leave the device. The layout is built for touch, and the Run button stays pinned to the bottom of the screen while you work. What changes on a phone is memory — there's much less of it, so the size limits are halved: the tool stops at files over about 1 GB, and it refuses re-encodes over 500 MB instead of letting the tab crash mid-run. Trimming, remuxing and extracting audio stay cheap, so those are the jobs a phone handles best. For a long video or a heavy encode, send the same command to the Rendi API; that works from a phone just as well.

That's a pixel-format mismatch. When a video isn't encoded as yuv420p, some players and browsers can't display it and fall back to green or garbled frames. Every MP4 our tools re-encode already sets -pix_fmt yuv420p, so you won't hit this here — and operations that copy the video stream untouched keep whatever format already played. If you write your own command in the terminal, add -pix_fmt yuv420p and it'll play everywhere.