MP4 Video Compressor
Make a video smaller without uploading it anywhere. Choose Light, Medium or Strong compression, or set a target size — for example under 25 MB for an email attachment — and the tool works out the bitrate and resolution for you.
Also: MKV to MP4 converter · AVI to MP4 converter · MOV to MP4 converter · WebM to MP4 converter · FLV to MP4 converter · TS to MP4 converter · WMV to MP4 converter · MPEG to MP4 converter · 3GP to MP4 converter · M4V to MP4 converter · MOD to MP4 converter · VOB to MP4 converter · MTS to MP4 converter · OGV to MP4 converter · RM/RMVB to MP4 converter · MXF to MP4 converter · Video to MP3 extractor · MP4 to GIF converter · Video format converter
Click to choose a video, or drag and drop
Choose an MP4 video — MOV, MKV, AVI, WebM and most other formats work too. Stays on your device.
Your video is converted entirely in your browser and is never uploaded. The converter engine (ffmpeg, ~32 MB) is downloaded once and cached by your browser.
Frequently asked questions
How do I compress a video to a specific size, like under 25 MB?
Choose Target file size, then type the size or click 8, 10, 25, 50 or 100 MB. The tool divides that size by the video’s length to work out the video bitrate, and lowers the resolution when needed so the picture stays sharp. The result is usually within a few percent of the target; if it comes out slightly over, lower the target by the percentage shown and run it again.
How much smaller will my video get?
It depends on how heavily the video is already compressed. Phone and screen recordings are usually large and shrink a lot; a video that has already been compressed shrinks less. Medium (720p, CRF 28) typically cuts a phone video to a fraction of its size. Strong goes further at some cost in sharpness.
Will compressing reduce the quality?
Yes, a little, because compression removes detail you are unlikely to notice. Two things control it: the CRF number (higher means smaller and softer) and the resolution. For the best quality at a given size, keep the resolution reasonable instead of using a very high CRF.
Why did my compressed video come out about the same size or bigger?
If the original is already efficiently compressed, there is little left to remove, and re-encoding can even make it larger. Choose the Strong preset, a lower resolution or a target size, and the result will be smaller. This tool can only produce H.264 video, not the more efficient H.265.
Can I compress other formats, like MOV or MKV?
Yes. Any video that opens here is re-encoded to a smaller H.264 MP4, so MOV, MKV, AVI, WebM and the rest all work. Surround audio is downmixed to stereo to save more space.
Is my video uploaded anywhere?
No. The conversion runs entirely in your browser using ffmpeg compiled to WebAssembly. Your video never leaves your device. Only the converter engine itself (about 32 MB) is downloaded, once, and cached by your browser.
What do CRF and bitrate mean?
CRF (constant quality) lets the encoder spend as many bits as each scene needs: lower numbers mean better quality and bigger files, around 18 looks near-lossless, 23 is the default and 28 is noticeably smaller. A target bitrate instead aims for a fixed number of kilobits per second, which gives a predictable file size but variable quality.
Why is re-encoding slow, and is there a size limit?
Re-encoding runs on a single CPU thread inside the browser (H.264 only), so it is usually near real-time speed or slower for HD. The finished MP4 also has to fit in browser memory, which in practice limits output to roughly 1 to 2 GB. For a long movie, use Fast remux, trim it, or copy the generated command and run it with ffmpeg on your own computer.
What happens to subtitles?
MP4 supports text subtitles only. SRT, ASS/SSA and WebVTT tracks are converted to the MP4 text format, and you can also save a track as a separate .srt file. Picture-based subtitles from Blu-ray or DVD (PGS, VobSub) cannot be converted.