Video Compressor
Shrink a video file by real H.264 encoding, with the actual size saving measured and reported before you download.
Convert with this tool
or choose a file from your device — it is processed in this tab and never uploaded
Accepted: MP4, MOV, MKV, AVI, WebM, M4V, FLV, WMV
Files stay on your device. There is no upload, no queue and no watermark, so a conversion works even with the network switched off after the page has loaded.
Supported formats & processing
| Accepted input | MP4, MOV, MKV, AVI, WebM, M4V, FLV, WMV |
|---|---|
| Produced output | MP4 with H.264 video and AAC audio at a reduced size |
| Processing | FFmpeg.wasm (video engine, downloaded on first use) |
| Upload required | No — the file is read locally and never transmitted |
How to use this tool
- Add the video and note the original sizeIt is shown next to the file name straight away.
- Set the CRF target28 for the smallest sensible file, 26 for a balanced one, 23 when quality matters.
- Downscale the resolutionGoing from 4K to 1280 px wide typically halves the file again.
- Lower the audio bitrate128 kbps AAC is transparent for most content; 96 kbps is fine for dialogue.
- Convert and read the savingThe percentage change is calculated from the real output size.
About this tool
Video files grow quickly, and the two most effective ways to shrink one are to reduce the resolution and to give the encoder a lower quality target. Both are here, along with a third lever that is often overlooked: the audio bitrate, which is easy to cut from 320 kbps to 128 kbps with almost no perceptible change.
The CRF slider is the main control. Constant Rate Factor tells the encoder how much detail to discard; 23 is the default balance, 28 gives a much smaller file with visible softness on fine texture, and 18 is close to transparent. The result card reports the original size, the new size and the percentage change so the trade is visible.
Features
- Real H.264 re-encoding, not a container swap
- CRF quality control with plain-language guidance per setting
- Resolution downscaling to 1280, 854 or 640 px wide
- Frame-rate reduction to 30 or 24 fps for further savings
- Audio bitrate control down to 96 kbps, or audio removed entirely
- Original, new and percentage size change all reported
Frequently asked questions
How much smaller will the file be?
That depends entirely on the source. A high-bitrate 1080p file compressed to CRF 28 at 1280 px wide often shrinks by 60–80 percent. An already-efficient file may shrink by much less, and it is possible to make a file larger if the source was already heavily compressed.
Why did my compressed file get bigger?
The source was already encoded efficiently. Try a higher CRF, downscale the resolution, or reduce the frame rate. The result card warns you when the output is larger than the input.
Is the audio re-encoded too?
Yes, to AAC at the bitrate you select. That is usually a saving in itself; original audio is often encoded at 320 kbps or higher.
Can I compress without losing any quality?
Not meaningfully. Lossless video codecs exist but they produce very large files. The practical approach is to pick the CRF that keeps the artefacts below what you can see.