How to compress a video
- Add your video. Click the upload box or drop an MP4, MOV, WebM, MKV or AVI file. The original plays in the preview so you can check you picked the right clip.
- Choose a level. High Quality (CRF 23) keeps the most detail, Balanced (CRF 28) suits most sharing, and Max Compress (CRF 32) gives the smallest file with visibly softer detail.
- Compress and compare. The first run downloads the FFmpeg engine (about 25 MB, then cached by your browser). The result shows the original size, the new size and the saving, with a preview of the compressed clip.
- Download. Save the MP4. If the new file is not smaller, the tool says so and hides the download, because your original is already the better file.
What the three levels actually change
The tool re-encodes the picture with the H.264 codec using a constant rate factor (CRF). CRF sets a target quality rather than a fixed size: each step of about six CRF points roughly halves the bitrate, so CRF 32 files are usually much smaller than CRF 23 files of the same clip. The frame size and frame rate stay the same as the source, and audio is re-encoded to AAC.
| Level | CRF | Best for |
|---|---|---|
| High Quality | 23 | Screen recordings with small text, footage you will edit again |
| Balanced | 28 | Messaging apps, email attachments, social posts |
| Max Compress | 32 | Previews and drafts where size matters more than detail |
Why some videos barely shrink
Recent phones already record efficient H.264 or HEVC video. Re-encoding such a clip at a similar quality cannot remove much more data, and an HEVC original can even come out larger as H.264. Screen recordings, exports from editing apps at high bitrates, and old AVI files usually shrink the most. If you need a much smaller file, try Max Compress, trim the clip first with the Video Cropper, or extract only the sound with Video to MP3.
How your file is handled
The page loads the open-source FFmpeg engine compiled to WebAssembly from a public content network, then reads your video with the browser's File API. Encoding happens in the browser tab and the result is offered as a download; the video itself is not sent to FastSaveMedia. Closing the tab clears it from memory.
Speed and device limits
The engine runs on a single processor core so that it works in every modern browser, including Safari on iPhone and iPad. Expect a one-minute 1080p clip to take a minute or more on a laptop and longer on a phone. Keep the tab in the foreground while it works, and close other heavy tabs for files over 100 MB.