Video Converter
Convert video in the browser
Convert between MP4 and WebM, scale the resolution, set the bitrate, trim, and mute — using the codecs your browser already has.
Video Converter
Runs in your browser · nothing uploadedPlays everywhere, including older phones, televisions and editing software.
01 — How to use Video Converter
02 — Getting good results
03 — Questions
No. Decoding and encoding both run in your browser using the codecs it already ships with. The file never leaves your machine, which matters for recordings of meetings, family footage and anything under an NDA.
It needs the WebCodecs API, available in Chrome, Edge and Safari 16.4 or later. Firefox support is still partial. The tool checks before it starts and says so plainly if a format cannot be encoded here, rather than failing halfway through.
The converted file is assembled in memory until you save it, and a browser tab has far less memory to work with than a desktop application. Ten minutes at a sensible bitrate stays comfortably inside that. For longer material, trim it into parts or use a desktop encoder such as HandBrake.
Browsers do not expose a video’s frame rate without parsing the container, and guessing would quietly produce the wrong one. Choose the rate explicitly instead — 30 suits almost everything, 25 matches European broadcast, 24 is film, and 60 is for fast motion such as games.
It is decoded, trimmed to the same window as the video, and re-encoded as AAC for MP4 or Opus for WebM. Choose Mute to drop it. If the browser has no encoder for that audio format, the video still converts and the result says the audio was dropped.
04 — More about Video Converter
What a video file actually contains
A video file is a container — MP4, WebM, MOV — holding one or more compressed streams, usually a video track and an audio track, together with an index that says where each frame lives and when it should be shown. The container and the codec are separate choices: H.264 is a way of compressing pictures, MP4 is a way of packaging them. Converting therefore means decoding each stream back to raw frames and samples, optionally changing them, compressing them again with the target codec, and packaging the result in a fresh container with a fresh index.
How modern video compression works
Consecutive frames are mostly the same, and codecs exploit that ruthlessly. A keyframe is compressed on its own, like a photograph; the frames after it are stored as differences from the frames around them — this block moved two pixels left, that one got slightly brighter. That is why video compresses so much better than a sequence of images, and why seeking lands on keyframes: to show an arbitrary frame, a player has to start from the last keyframe and apply every difference since. This tool places a keyframe every two seconds, which keeps the file seekable without the size cost of making every frame a keyframe.
H.264, VP9 and the choice between them
H.264 dates from 2003 and is supported by essentially every device made since, usually in dedicated hardware, which is why it remains the safe default for anything that must play everywhere. VP9, released by Google in 2013, achieves the same visual quality at roughly two-thirds of the bitrate and plays in every current browser, but older televisions and editing software may not open it. VP8 is VP9’s predecessor and is included because some browsers can encode it where they cannot encode VP9.
Why this uses the browser’s own codecs
Most web-based converters either upload your file to a server or run a WebAssembly build of ffmpeg, which is around thirty megabytes downloaded by every visitor and licensed under the GPL. This tool uses WebCodecs instead, which exposes the encoders and decoders the browser already contains for playing video. The download is nothing, nothing is uploaded, and encoding is frequently hardware-accelerated. The trade is that the formats available are the ones the browser provides — which is why the tool checks support before starting rather than after.
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where this came from.
Same shell, same shortcuts, same promise: nothing leaves your browser.