Convert Video to H.264 MP4

Convert any video to universally-playable H.264 MP4

Some videos just won't play — a .webm that Safari refuses, a 10-bit HEVC clip an old TV can't decode, a 4:2:2 export a phone chokes on, an .mkv a web page won't accept. The fix is almost always the same: re-encode to the one video form that decodes essentially everywhere — H.264 video in an MP4 container, 8-bit 4:2:0 (yuv420p) chroma, with +faststart and AAC audio.

This tool always applies that exact recipe. Drop in any clip and you get a normalized .mp4 that plays in every modern browser, phone, TV, and editor. Everything runs locally with ffmpeg compiled to WebAssembly — your file is never uploaded to a server.

What "make it play anywhere" actually means

• H.264 (libx264) — the most broadly hardware- and software-decoded video codec on earth.
• yuv420p — forces 8-bit 4:2:0 chroma. Many players can't decode 10-bit, 4:2:2, or 4:4:4; this normalizes them down so the picture always shows.
• +faststart — moves the MP4 index to the front so the video starts playing before it fully downloads (progressive web playback).
• AAC audio — the universally-supported audio codec (silent inputs stay silent — no track is invented).

Profile — the compatibility dial

• High (default) — best compression; plays on every browser and device made since ~2012. Use it unless you have a reason not to.
• Main — a touch more legacy reach, marginally larger files.
• Baseline — the widest possible reach: no B-frames, no CABAC, for genuinely old or embedded players. Largest file for the same quality; only reach for it when something refuses High.

Worked example

Take a 1-second clip.webm (VP9 video + Opus audio) that won't play in Safari. Leave Profile on High and Quality at 75, drop the file in, and out comes clip.mp4: same 64×64 frame and ~1s duration, but now H.264 High / yuv420p with AAC audio — plays in Safari, on an iPhone, and in a plain <video> tag. Pick the Maximum compatibility preset instead and the same clip comes out as Constrained Baseline for old hardware.

Limits

• Input and output are each capped at 10 MiB — compress or trim longer clips first (see the video-compress and video-trim tools).
• Output is always H.264/MP4. To target WebM/VP9 instead use video-transcode; to shrink a file use video-compress; to change the frame size use video-resize.
• This tool always re-encodes (that's the point). If your clip is already H.264/HEVC in a .mov and you only want to change the container without re-encoding, use mov-to-mp4 for a lossless remux.

FAQ