Compress MP4 files and keep them MP4
The MP4 compressor takes an MP4 or M4V video and gives you back a smaller MP4 that plays in the same places. Set a size in megabytes or a quality level, choose H.264 for maximum compatibility or HEVC for a smaller file at similar quality, and the video is re-encoded in your browser. The AAC soundtrack is copied untouched unless you pick a lower audio bitrate.
MP4 is what phones, cameras, screen recorders and editing apps export by default — and those recorders favour high bitrates so nothing is lost while capturing. Re-encoding at a bitrate that suits the picture, often combined with a lower resolution, is where the savings come from. Nothing is uploaded: the encoding runs on your device with WebCodecs and the Mediabunny library (MPL-2.0).
How to use the MP4 Compressor
- Drop your MP4 on the box or click to browse. Check its duration, resolution, frame rate, codec, bitrate and audio.
- Choose Target file size and enter the MB you need, or Quality and set the slider; the estimated size and bitrate update immediately.
- Pick H.264 or HEVC, and if you like a lower Max resolution, Frame rate or Audio bitrate.
- Press Compress video and follow the progress bar.
- Play the original and the new MP4 side by side, then press Download MP4.
MP4 Compressor features
Stays a web-ready MP4
The output is a standard MP4 with its index (the moov box) at the start of the file, so players can begin before the whole file has downloaded.
H.264 or HEVC
H.264 plays everywhere. HEVC is written with the hvc1 tag that Apple’s players expect.
Audio copied, not re-encoded
AAC audio is copied packet for packet unless you choose a bitrate, so the sound keeps its original quality.
Target size with automatic retry
In target mode a pass that comes out too big is encoded again at a corrected bitrate.
Honest results
If the new MP4 would be bigger than the one you started with, you are told to keep the original.
Why MP4 files get so big — and what shrinks them
File size is simply bitrate × duration. A recorder writing 16 Mbps produces 16 ÷ 8 × 60 = 120 MB every minute, whatever is in the picture. For comparison, YouTube’s published upload recommendations ask for 8 Mbps for 1080p at 24–30 fps and 5 Mbps for 720p — and those are for uploads YouTube re-encodes anyway. Many phone and screen recordings therefore carry far more bits than they need for sharing.
Three settings shrink an MP4: a lower bitrate (the target size or the quality slider), fewer pixels (Max resolution) and fewer frames (Frame rate). Dropping from 1080p to 720p removes more than half the pixels, which lets a modest bitrate look clean. The table converts bitrate to megabytes per minute.
| Total bitrate | MB per minute | Typical use |
|---|---|---|
| 1 Mbps | 7.5 MB | Small 480p clip, talking head |
| 2.5 Mbps | ≈ 19 MB | 720p for messaging |
| 5 Mbps | 37.5 MB | Good 1080p H.264 |
| 8 Mbps | 60 MB | High-quality 1080p |
| 16 Mbps | 120 MB | Typical camera-original 1080p |
H.264 or HEVC inside an MP4?
H.264 (AVC) is the safe choice for anything you will share: messaging apps, email, websites, older TVs and video editors all accept it. HEVC (H.265) needs roughly 40% less bitrate for similar quality — the rule of thumb this tool uses — so at the same file size it looks noticeably cleaner. The trade-off is compatibility: Apple devices and most recent Android phones play it, but some Windows PCs need the HEVC Video Extensions, and some browsers and apps can’t play it at all.
There are two ways to tag HEVC in an MP4, hvc1 and hev1. Apple’s players expect hvc1, which is what this tool writes. Encoding HEVC also needs hardware support, so if it is marked ✕ your browser can only offer H.264.
What is kept and what is not
- Kept: the main video track (re-encoded), every audio track (copied or re-encoded), the rotation of phone videos and descriptive tags such as the title.
- Not copied: text subtitle tracks, chapter markers and timecode tracks. The tool lists any it finds before you compress, so nothing disappears silently.
- Colour: HDR videos are converted to standard dynamic range, because the browser encoders used here write 8-bit video.
- Older codecs: an MP4 with MPEG-4 Part 2 (Xvid) video, or HEVC in a browser that can’t decode it, is first decoded with ffmpeg.wasm (GPL-2.0-or-later) — a 32 MB download you have to confirm.
- To cut the video shorter first, use Trim Video; to keep only the soundtrack, use Video to Audio.
MP4 Compressor FAQ
How do I compress an MP4 without losing quality?
Every re-encode loses a little detail, but you can keep it invisible: use Quality in the upper half of the slider, keep the resolution, and compare both versions side by side before downloading. The audio is copied, so it does not change at all.
Should I choose H.264 or HEVC for my MP4?
Choose H.264 if the file is going to other people, websites or older devices. Choose HEVC for clips you keep on modern phones and computers, or when you need the best quality at a fixed size.
Will the compressed MP4 play on my phone, TV or in a messaging app?
An H.264 MP4 is the most widely accepted video file there is. HEVC plays on most phones from recent years, but some apps and older TVs re-encode or reject it.
Why is my MP4 still large after compressing?
Long videos need many bits even at a modest bitrate. Use Target file size to set the size directly, lower the resolution to 720p, cap the frame rate at 30 fps, or check the numbers first with the video bitrate calculator.
Does the MP4 compressor keep subtitles and chapters?
No. Text subtitle tracks and chapters are not copied; the tool lists them before you start. Every audio track is kept.
Are my MP4 files uploaded to a server?
No. The MP4 is read and encoded by your browser on your own device, and the result is created in memory for you to download.