OneTaskBy Tim King · Updated
MP4 Compressor
Shrink Video to a Target Size in MB, No Upload
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How the MP4 Compressor works
This MP4 compressor shrinks a video to fit under a target size in megabytes. Set the target, drop in the file and download an MP4 that fits. The page works out the bitrate from the clip's length, re-encodes it as H.264 and, if you choose, scales it down or removes the sound. The result plays on any device. It runs faster than real time on your own hardware, and nothing is uploaded.
MP4 compressor: how a target size becomes a bitrate
A video's size is its bitrate multiplied by its length. So to hit a size, the page divides the target by the duration. It keeps 3 percent back for the MP4's own structure and sets aside 128 kbps for the sound if it is kept. The rest goes to the picture. A 2-minute clip with a 25 MB target gets about 1.5 Mbps of video, which looks good at 720p and acceptable at 1080p.
If the target is too small for the length, the page says so and suggests the smallest size that works. Below about 100 kbps, video turns to mush at any resolution.
Choosing the resolution
Bitrate spread over fewer pixels looks sharper. As a rough guide for H.264:
- 1080p needs about 4 Mbps or more to look clean.
- 720p looks good from about 1.5 to 2 Mbps.
- 480p is fine from about 0.8 Mbps.
- 360p holds up down to about 0.4 Mbps.
If the bitrate the page works out is below the guide for your clip's resolution, choose a lower one. A sharp 720p video beats a blocky 1080p one. Removing the sound frees 128 kbps for the picture, which matters on very small targets.
Common size limits
- Discord: 10 MB for free accounts.
- Email: about 20 to 25 MB once attachments are encoded, for Gmail and Outlook.
- WhatsApp: around 100 MB for videos sent as media.
These limits change, so check the current one where you are sending.
This page or the WebM video compressor?
This page writes H.264 MP4 using WebCodecs, the browser's interface to the device's video hardware. That runs faster than real time and plays everywhere. The video compressor uses the browser's recorder instead. It plays the clip through in real time and writes WebM, which suits browsers without WebCodecs. To cut the clip shorter first, use the video trimmer. A shorter clip gets more bitrate for the same size.
FAQ
Why is my file slightly under the target?
The page aims a little low so the file never goes over. Encoders vary the bitrate from scene to scene, and the 3 percent margin absorbs that. A file 5 to 10 percent under the target is normal.
Can I compress without losing quality?
Not to a smaller size. Compression drops detail the eye is least likely to miss, and a lower target drops more. Choose the largest target your destination allows, and lower the resolution before the bitrate gets too thin.
Does it keep the original frame rate?
Yes. Only the bitrate and, if you choose, the resolution change. Frame rate, length and aspect ratio stay the same, so a 60 fps clip stays at 60 fps and plays just as smoothly.
Is the video uploaded?
No. The compression runs in this browser tab and the file never leaves your device. The page only needs the internet to load itself and the converter library, and the finished file is saved straight from memory to your downloads.
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