compress video
Re-encoded on your own machine, at 720p and a quality you can see.
Up to 200 MB. H.264 at CRF 28, capped at 720p. Expect two to four times the length of the clip: this is your own processor, not a server farm.
Checking whether the video and audio converter is already on this device
0%The short answer
The video is re-encoded as H.264 at a constant quality of 28 and capped at 720p, which is where most of the saving comes from and what keeps the encode inside a browser tab's memory. It runs here rather than on a server, so a private clip never leaves the machine, and the 31 MB converter is kept for next time.
H.264 at a constant quality of 28, capped at 720p. Most of the saving comes from the resolution, and it is also what keeps the encode inside a browser tab's memory.
The formula
ffmpeg -i video -vf scale='min(1280,iw)':-2 -c:v libx264 -preset ultrafast -crf 28 -threads 2 -c:a aac -b:a 128k out.mp4
Worked examples
- A phone recording
- usually 40–60% smaller
- An already-compressed export
- little to gain
- A screen recording
- large gains, text stays readable
Reference table
| CRF | Quality | Use it for |
|---|---|---|
| 18 | Visually lossless | Archiving, further editing |
| 23 | Default, very good | Anything you care about |
| 28 | Good | Sharing, uploading, email |
| 32 | Visibly soft | When only the size matters |
How to use it
- 01Let the converter loadIt starts in the background when you open the page and is kept for next time.
- 02Drop the video inRe-encoding is real work: expect roughly the length of the video on a decent laptop.
- 03Save the smaller fileThe panel shows the new size and the time it took.
Also searched for
Searches that land here include compress video, reduce video size, make video smaller, video compressor and shrink mp4.
Making a video smaller
Quality target, not size target
Asking for a specific file size means the encoder guesses a bitrate and spends it evenly, which wastes bits on still frames and starves the busy ones. Asking for a quality level instead lets it spend where the picture needs it. That is why this page has no "compress to 10 MB" box: the honest control is quality, and the size is the result.
Where the savings come from
Most footage from a phone is encoded quickly, at a high bitrate, by hardware that is optimising for speed and battery rather than size. Re-encoding it more carefully on a machine that is not in a hurry finds a great deal of slack. A screen recording is the extreme case: huge areas of the frame do not change at all between frames, and a careful encoder spends almost nothing on them.
When not to bother
If the file has already been through a messaging app or a social platform, it has been compressed hard already. Running it through again mostly costs quality rather than size, and the honest answer is that there is nothing left to reclaim.
Questions people ask
How much smaller will my video be?
Usually between forty and sixty per cent for something straight off a phone, and much more for a screen recording. Almost nothing for a file that has already been compressed hard — an Instagram download, say — because the detail that CRF 28 would discard has already gone.
Why is it slower than the online converters?
Because those are running on a server with hardware encoding, after you have uploaded the file and waited in a queue. This is your own processor, in a browser tab, at roughly a third of native speed. It is a real trade: your video never leaves the machine, and you pay for that in minutes.
What does CRF 28 mean?
Constant Rate Factor: the encoder aims for a consistent quality rather than a consistent bitrate, so a still scene costs few bits and a busy one costs many. Lower numbers are better quality and bigger files. 18 is visually lossless, 23 is the default, 28 is the sweet spot for sharing.