Video Compressor
Compress and shrink video files locally in your browser, no upload, no quality wall.
Loading Video Compressor… If nothing happens, please enable JavaScript.
A video compressor reduces the file size of a video by re-encoding it at a lower bitrate, so a clip that was too big to email, upload or store becomes manageable while still looking good. Most of a modern video file is the encoded picture data; by asking the encoder to spend fewer bits per frame, you trade a small, often invisible, amount of visual detail for a dramatically smaller file. This tool uses the H.264 codec in an MP4 container, the most widely compatible combination, and lets you choose how aggressively to compress.
Frequently asked questions
Is my video uploaded anywhere?
How much smaller will my file get?
Will compressing reduce the quality?
What format does it output?
Is there a maximum file size?
Why is it slower than an app on my computer?
Does it also reduce the resolution?
Does it work offline?
About Video Compressor
Everything happens inside your browser using a WebAssembly build of FFmpeg. Your video is read from your device, compressed locally, and returned as a download. Nothing is ever uploaded, which makes it safe for personal recordings, work footage, or anything you would rather not send to a third-party server. It also means there are no file-size caps imposed by an upload limit, only the practical limits of your device's memory.
The quality setting controls the constant rate factor (CRF), the knob that balances size against quality. A lower CRF keeps more detail and produces a larger file; a higher CRF compresses harder and produces a smaller one. Light keeps near-original quality, Medium is a balanced everyday choice, and Strong squeezes the file as small as is reasonable. Because the encoder works frame by frame, results depend on the content: a static talking-head clip compresses far more than fast-moving action or noisy footage.
As with all the video tools here, compression runs single-threaded so it stays compatible with the rest of the site and keeps your data private. That makes it slower than a desktop encoder and memory-hungry on very large inputs. For short and medium clips it is quick and convenient; for multi-gigabyte files, compress in segments or use a desktop tool.
Why a phone video is so much bigger than it needs to be
Phones and cameras prioritise capture speed and quality over file size. They often record with a high, near-constant bitrate and light compression so the device can write frames quickly without taxing its processor, which is why a few minutes of 4K can run to several gigabytes. That footage has a lot of redundancy a more careful encoder can remove.
The key idea behind modern compression is that consecutive frames are mostly similar. Instead of storing every frame in full, codecs like H.264 store occasional complete frames (keyframes) and then describe the others as differences from their neighbours, motion vectors and small corrections. A static scene barely changes between frames, so it compresses enormously; fast motion and visual noise change a lot, so they need more data.
The constant rate factor (CRF) used here tells the encoder to target a consistent visual quality rather than a fixed size, spending bits where the eye notices them and saving them where it does not. This perceptual approach is why a well-chosen CRF can halve a file with no obvious difference, and it is the same principle that lets streaming services deliver high-quality video over ordinary home connections.