Compress a video to the size you need
Drop an MP4 or MOV, choose where it has to fit (Discord, email, WhatsApp or any size in MB) and your browser re-encodes it to land just under that size. The video never leaves your device. It shows the real size at the end and tells you if the target was missed.
Checking what your browser can do…
Why not just use any online compressor
- •Most online compressors upload your video to a server. This one does the work in your browser, so a private clip stays private and there is no upload wait.
- •You choose the size, not a vague quality slider. The page works out the video bitrate from the length and your target, keeps a few percent in reserve, and lowers the picture size when the target is tight.
- •It is free, has no watermark and needs no account.
What this tool does and does not do
- •Reads MP4, MOV and M4V files up to 1 GB (a warning appears above 300 MB). WebM, MKV and AVI are not supported.
- •Needs a browser with WebCodecs and an H.264 encoder: recent Chrome, Edge or Safari on a computer. HEVC (H.265) videos from phones work only where your browser can decode them.
- •Writes an H.264 MP4. The size is aimed, not guaranteed: it usually lands within a few percent, and the real size is shown with a clear message if it is over.
- •Quality per megabyte is below what two-pass tools such as ffmpeg or HandBrake achieve, because the browser's encoder works in a single pass. It is built for getting under a limit quickly.
- •Sound that is already AAC is copied untouched. Other sound is re-encoded as AAC if the browser can, otherwise it is left out and you are told.
- •Frame rate is kept as it is. HDR videos are not tone-mapped and can look flatter. Date, location and other metadata are not copied.
- •Speed depends on your device. Laptops with hardware encoding are often near real time; phones and old computers are slower. Keep the tab open and in front.
Other ways to shrink a video
- •On a Mac, QuickTime Player > File > Export As lets you pick 1080p, 720p or 480p. It does not aim for a size.
- •For the best quality at a given size, use ffmpeg with two passes. The video size calculator below gives you the exact command.
Questions
- Is my video uploaded?
- No. Your browser reads, re-encodes and saves the video itself. The only things downloaded are the page and two small code files (about 230 KB) that read and write MP4 files.
- How accurate is the size?
- Usually within a few percent. The page keeps about 5% of the budget in reserve for the container and for the encoder landing a little high. If the file still ends up over, it says so and by how much, so you can try again with a smaller picture size.
- How do I get a video under the Discord, email or WhatsApp limit?
- Pick the destination in the list. The target is set just under its free limit. Check the current limit of the service: they change, and WhatsApp in particular reports different numbers on different pages.
- Why is it slow?
- Every frame is decoded and encoded again. A laptop with a hardware encoder can be quick, a phone or an old PC much slower, and a long 4K video takes a while on any device. The page shows progress and the time left, and you can stop at any time.
- Why does my phone video not open or compress?
- Many phone videos use HEVC (H.265). Safari and some Chrome and Edge setups can decode it, others cannot. If yours cannot, the page says so before doing any work. Try Safari, or a computer with hardware video support.
- Why is the result bigger than my original?
- Phone videos are often already compact. Asking for a bigger size than the original, or a high quality level, can make a larger file. In target mode, choose a size below the original.
- Can I compress WebM, MKV or AVI?
- Not here. This page reads MP4, MOV and M4V only. Convert the file to MP4 first, or use ffmpeg.
- Will the sound stay?
- Yes if it is AAC, which almost all MP4 and MOV files use: it is copied without any loss. Other sound is re-encoded to AAC where the browser allows it. You can also remove the sound to save space.
How it works
The page opens your file with mp4box.js, decodes it with your browser's own video decoder, re-encodes it with the browser's H.264 encoder, and writes the MP4 with mp4-muxer. Both libraries are separate files you can inspect, and nothing is sent out. Third-party notices