Compress a 4K video
4K at 60 fps off a phone runs 400–500 Mbps of pixels and lands around 350–400 MB per minute. Downscaling to 1080p removes three-quarters of those pixels before the encoder even starts, which is why it saves far more than turning quality down.
Compress a 4K video
Pick a quality level; the file comes out as big as this clip needs.
Choose a video or drop it here
Read by this page, never uploaded. MP4, MOV, MKV, WebM, AVI, WMV, FLV and more.
Resolution, frame rate, audio, codec
Nothing is uploaded
FFmpeg runs in this tab. Turn your Wi-Fi off after the page loads and it still works.
Hit an exact size
Say "under 25 MB" and the bitrate is solved for you, two-pass.
No account, no watermark
No sign-up, no email, no logo burned into your video.
No file-size cap
No 100 MB paywall. The only limit is your browser's memory, around 2 GB.
What 4K actually costs
4K is 3840 × 2160 — 8.3 million pixels per frame, four times 1080p. At 60 fps that is half a billion pixels a second, and phones record it at 45–50 Mbps to keep it clean. In practice:
| Source | Per minute | Ten minutes |
|---|---|---|
| iPhone 4K60 (HEVC) | ~400 MB | ~4 GB |
| iPhone 4K30 (HEVC) | ~190 MB | ~1.9 GB |
| GoPro 4K60 | ~450 MB | ~4.5 GB |
| Drone 4K30 (H.264) | ~750 MB | ~7.5 GB |
Downscale before you do anything else
Dropping 4K to 1080p removes 75% of the pixels before the encoder starts. Nothing in the quality slider comes close to that, and for anything watched on a phone, a laptop or in a chat app, nobody will be able to tell — 1080p is more resolution than most of those screens will show anyway.
Keep 4K only when the destination genuinely uses it: a 4K television, a YouTube upload you want in 2160p, or footage you are going to edit and crop into later.
Be realistic about doing this in a browser
This is the honest limit of the in-browser tool. WebAssembly caps a tab near 2 GB of memory, and a re-encode needs roughly three times the file's size free, so:
- Under ~300 MB: comfortable. A minute or two of 4K.
- 300 MB – 1 GB: works, but expect minutes, not seconds. Close other tabs first.
- Over ~1 GB: use the iPhone app instead. It has no memory ceiling and the hardware encoder is an order of magnitude faster than one WebAssembly thread.
Time scales with output pixels, so downscaling to 1080p does not just make a smaller file — it makes the job roughly four times faster. If you are compressing 4K here, choose 1080p and the wait becomes reasonable.
H.265 for archiving
If the goal is to store the footage rather than send it, H.265 at High quality keeps 4K detail at roughly 30% less size than H.264. It is slow to encode in a tab — budget several times the clip's length — but for a keeper, it is the right trade.
How it works
Pick your video
It is read straight from your disk by this page. No upload, no queue, no account.
Choose a quality level
Balanced is visually indistinguishable on a phone or laptop at normal viewing distance.
Compress in the tab
FFmpeg runs in WebAssembly on your own machine. The first run downloads a 31 MB engine, once per browser.
Download it
The result is handed back as a file. Nothing was sent anywhere, so there is nothing to delete afterwards.
Compress for a specific limit
Compress a video for email
Targets 20 MB by default.
Open the compressor →Compress a video for Discord
Targets 9 MB by default.
Open the compressor →Compress a video for WhatsApp
Targets 15 MB by default.
Open the compressor →Compress a video to 8 MB
Targets 7.5 MB by default.
Open the compressor →Compress a video to 25 MB
Targets 24 MB by default.
Open the compressor →Compress an MP4
Quality-based, no target to pick.
Open the compressor →Compress a MOV file
Quality-based, no target to pick.
Open the compressor →Compress a video for Instagram
Quality-based, no target to pick.
Open the compressor →Reduce a video's file size
Quality-based, no target to pick.
Open the compressor →Questions people actually ask
Short answers here, the full story in the guides.
Is my video uploaded to a server?
No. The compressor is FFmpeg compiled to WebAssembly and it runs inside this browser tab. Your file is read from disk by the page, processed in memory, and handed back to you as a download. You can load the page, disconnect from the internet, and compress anyway — which is the simplest proof there is.
Does compressing a video lose quality?
Yes, always — compression works by throwing information away. The honest question is whether you can see it. At a sensible bitrate for the resolution, most people cannot tell on a phone or laptop screen. Anyone promising "no quality loss" is describing the perception, not the file.
How do I compress a video to an exact size?
Switch the tool to Target size and type the number. It reads the clip's duration, subtracts the audio budget, solves for the video bitrate that fits, and encodes two-pass so the result lands under the target rather than near it.
Is there a file size limit?
No limit we impose, but a browser tab is bounded by WebAssembly's ~2 GB of memory, and a re-encode needs roughly three times the file's size free. Files up to a few hundred MB are comfortable. Above about 1 GB, the iPhone app is the better tool.
Is there a watermark?
No. No watermark, no logo, no intro frame, no account, and no upload cap to unlock by paying. The output is your video, compressed.
Which format should I compress to?
MP4 with H.264 video and AAC audio, unless you have a specific reason not to. It plays on effectively everything. H.265 gives you a smaller file at the same quality but encodes much slower here and is refused by some uploaders and older devices.
Compressing on a phone?
The iPhone app does this on the device, with the hardware encoder.