MP4 Converter

MP4 with H.264 video and AAC sound is the one combination that plays on every phone, browser, smart TV, car screen and video editor. This converter turns any video into that MP4. If the video is already H.264 it is copied without re-encoding, so nothing is lost; otherwise it is re-encoded with x264. Presets cover the usual sizes, plus a mode for old phones and TVs that only understand the simplest H.264. It all happens in your browser — nothing is uploaded.

How to use this tool

1. Choose one or more videos in any format.
2. Pick a preset: original size, 1080p, 720p, 480p, or "Old phones & TVs".
3. Choose the quality used when re-encoding.
4. Press Calculate and download the MP4 files.

Formula

MP4 = H.264 (yuv420p, 8-bit) + AAC, with the index at the front (faststart)

8-bit 4:2:0 colour (yuv420p) is what hardware decoders support; 10-bit or 4:4:4 sources are converted. Faststart moves the index to the start of the file so a web player can begin before the whole file has downloaded. The old-device preset uses the baseline profile at level 3.0 (no B-frames, at most 720 × 480 at 30 fps) with stereo AAC.

Example

A 2-minute 4K clip from a drone (HEVC, about 700 MB) with the 720p preset at CRF 22 becomes roughly 60–120 MB of H.264, which uploads quickly and plays on any laptop. With "Original size" and an H.264 source, the file would simply be repackaged in seconds.