Compress a video
Shrink a video file without uploading it anywhere. The whole thing runs on your own device, so there is no queue and no file size cap beyond your browser's memory.
What actually makes a video file smaller
File size is close to a simple product: bitrate multiplied by duration. Bitrate is how many bits per second the encoder spends describing the picture, and it is the dial that matters. A ten-minute clip at 10 Mbps is roughly 750 MB whether it is 1080p or 4K.
That is why this tool exposes quality rather than a target size. Behind each option is a CRF value — constant rate factor — which tells the encoder how much quality to preserve and lets the bitrate land where it needs to for that footage. High quality is CRF 23, Balanced is 28, Smallest is 32. Lower numbers look better and produce larger files.
How far you can push it depends entirely on the content. A person talking in front of a plain wall survives aggressive compression, because almost nothing changes between frames and the encoder has plenty to reuse. Handheld footage of rain, confetti, foliage or a crowd falls apart much sooner, because nearly every pixel changes every frame.
Nothing is uploaded
Most online compressors send your file to a server, put it in a queue, and hand back a download. That means waiting twice on your connection, and trusting a company’s retention policy with footage you may not want copied anywhere.
This tool runs FFmpeg compiled to WebAssembly, so the encoding happens in your own browser on your own processor. You can check that claim rather than take it: open your developer tools, watch the Network tab while you compress, and you will see no upload. Load the page, disconnect from the internet, and it still works.
The practical consequences are worth stating. There is no file size limit imposed by us, because your video costs us nothing to process. There is no queue, because you are not sharing a machine with anyone. There is no watermark and no paid tier.
Where the real limit is
Your device’s memory. The processing engine is 32-bit, which caps how much it can address, and video is large — a single uncompressed 4K frame is around 24 MB and several are in flight at once. A modern laptop handles large 4K files comfortably; a phone has considerably less headroom and will fail sooner. If an export stops, that is almost always why, and a shorter clip or a lower resolution will get through.
Trim before you compress
The cheapest size reduction is removing footage you do not need, and unlike compression it costs no quality at all in the part you keep. Most oversized files contain dead air at the start, a fumble at the end, or a long stretch nobody will watch. Cut those first with the video trimmer, then compress what is left.
One caveat: the relationship is not perfectly linear. Encoders spend more bits on complex, fast-moving footage, so if you cut a static intro and keep the action, the file shrinks by less than the duration suggests.
Always compress from the original
H.264 is lossy, so every decode-and-re-encode cycle discards a little more detail. Compress an export, then compress that, and the degradation compounds visibly. Going back to your source file each time is both faster and better. Our guide to reducing video file size covers the other levers — resolution, frame rate and codec choice — in more depth.
Frequently Asked Questions
How much smaller will my video be?
It depends on the footage and the quality you pick. Balanced typically lands around half the original size; Smallest can reach a quarter. A talking head against a plain background compresses far better than handheld footage of a crowd or falling leaves, because almost nothing changes between frames for the encoder to reuse.
Does compressing reduce quality?
Yes, some. Compression re-encodes the video, and H.264 is lossy, so every pass discards a little detail. High quality is close to invisible; Smallest is deliberately visible. What matters most is compressing from your original file rather than from a previous export, because the loss compounds each time.
Is there a file size limit?
We impose none, because your video is processed on your own device and costs us nothing. The real limit is your browser's memory. A modern laptop handles large 4K files comfortably; phones have much less headroom and will fail sooner on long clips.
Is my video uploaded anywhere?
No. The compressor runs FFmpeg compiled to WebAssembly, entirely inside your browser. Open your developer tools, watch the Network tab while you compress, and you will see no upload. You can also disconnect from the internet after the page loads and keep working.
Which formats can I compress?
MP4, MOV, WebM and MKV, with H.264, H.265, VP9 or AV1 video inside them. The output is always H.264 in an MP4, which is the most broadly playable combination. Some exotic files depend on what your specific browser can decode.
Why did my file get bigger instead of smaller?
Almost always because the source was already compressed harder than the setting you chose. Re-encoding an efficiently compressed file at a higher quality target produces a larger result. Pick a smaller setting, or trim unwanted footage instead, which reduces size at no quality cost at all.