Compress an MP4 file
Shrink an MP4 without installing programs or uploading it anywhere. You choose the final size and the tool adjusts resolution and bitrate to reach it with the least possible loss.
Your video is never uploaded: it is compressed inside your own browser.
Why compress it here
How to reduce the size of an MP4
Pick the MP4 file from your device.
Decide how small it should be: half, a specific size in MB, or the minimum.
Check the resulting resolution and press 'Compress'.
Download the reduced MP4.
What actually takes up space inside an MP4
MP4 is a container: a box holding a video track, an audio track and some metadata. The file size is decided not by the box but by what is inside it, and specifically by three things.
- Resolution. A 4K video has four times the pixels of a 1080p one, and that shows up directly in the weight.
- Frames per second. Recording at 60 fps doubles the number of images compared with 30 fps.
- Bitrate. How much data per second the codec spends. Phones record at very high bitrates because they assume you will edit the footage, not message it.
That last point is where the headroom lives. A phone video may run at 17 Mbps when 5 or 6 would look identical on an ordinary screen — that is what gets trimmed without anyone noticing.
Lowering the bitrate or lowering the resolution
These are the two levers and they do not behave the same. Lowering the bitrate while keeping the resolution preserves fine detail as long as there is enough data; once there is not, blocks and smearing appear in anything that moves. Lowering the resolution reduces detail uniformly, but what remains looks clean.
The tool uses both, in that order: first it spends the bitrate headroom while keeping the resolution — that is the first option in the list, the one you cannot see — and only drops resolution when the size you asked for does not fit any other way. When it does, it tells you which resolution: 720p, 480p, whatever applies. You will never see a bare "medium quality" with no number behind it.
The most profitable case: 4K to 1080p
If you have a 4K video destined for a phone, a messaging app or a website, dropping it to 1080p gives the best ratio of space saved to quality lost. The file shrinks enormously and on a phone screen the difference is hard to spot even side by side.
If your video is headed somewhere with a specific cap, go to its page: WhatsApp, email or Discord. And if quality is your main worry, here is exactly what gets lost.
Frequently asked questions
Why is my MP4 so big?
MP4 is only the wrapper; what takes up space is the video inside it. Three factors drive it: the resolution (4K is four times the pixels of 1080p), the frames per second (60 fps is twice the work of 30), and the bitrate the camera used, which on modern phones is very generous because they record for editing, not for sharing.
Is the result still an MP4?
Yes, and with H.264 and AAC inside, the most compatible combination there is: any phone, TV, editor or social network opens it without installing anything. We are not going to hand you back an exotic format that causes trouble later.
Can an MP4 be shrunk without re-encoding?
Only in very specific cases, and it gains almost nothing: changing container (MKV to MP4, say) can be done by copying the data as-is, but that moves the video without reducing its weight. To take up less space it has to be re-encoded, which is what this tool does. If changing the wrapper was the actual goal, use the converter.
How much can I shrink it before it shows?
It depends how it was recorded. A video fresh off a phone usually carries far more bitrate than it needs and takes a halving without any visible change. One that was already compressed — downloaded from a social network, for instance — has little headroom and shrinking it forces a resolution drop. That is why the first option is computed on your file rather than being a fixed percentage.
Does it work with 4K videos?
Yes, though they take longest because there is far more picture to decode. If you do not need the 4K, dropping to 1080p is the single most profitable reduction available: the file collapses and on a phone screen the difference is essentially invisible.