Why downscale 4K to 1080p?

Most playback (phones, web, smart TVs at viewing distance) doesn't benefit from 4K. The 1080p file is ~4x smaller, plays everywhere, edits faster, and uploads quicker. For delivery, 1080p is still the standard.

Will 1080p output look sharper than the 4K source?

Slightly, yes — the downscale uses lanczos resampling which sharpens edges. On a 1080p screen, properly downscaled 4K looks crisper than native 1080p captured by the same camera.

Does my 4K file get uploaded?

No. The page runs FFmpeg in your browser. Multi-gigabyte 4K files stay on your disk.

4K to 1080p — in your browser

Drop a 4K (or 8K) video here. Get back a 1080p MP4, roughly a quarter of the size. No upload, no signup, no watermark.

drop a 4K video here

or click to choose

Why downscale 4K?

File size. A 1080p H.264 file is roughly 1/4 the size of the 4K source at equivalent visual quality. A 10-minute 4K clip at 50 Mbps is 3.7 GB; the same clip at 1080p / 8 Mbps is ~600 MB.
Playback compatibility. Some phones, older TVs, and web players choke on 4K. 1080p plays everywhere.
Edit performance. Premiere, Resolve and Final Cut all scrub faster on 1080p proxies than native 4K. Many editors transcode 4K to 1080p proxies, edit, then conform back.
Upload speed. A 1080p delivery file uploads to YouTube in a quarter of the time.
Display reality. At normal viewing distance on a phone or laptop, the human eye doesn't resolve 4K. A well-downscaled 1080p actually looks sharper than native 1080p because the source has more detail to work with.

How the downscale works

We use FFmpeg's scale filter with the lanczos algorithm. Lanczos is the gold-standard for downscaling — preserves sharp edges, minimizes ringing, gentle on fine textures. The arithmetic happens in your browser, on your CPU.

The pixel math: 3840×2160 (4K UHD) → 1920×1080 (1080p) is exactly half resolution in each dimension. For odd 4K sources (DCI 4K at 4096×2160, or cinema 4K crops), the tool keeps aspect ratio and lands at the nearest 1080p-class output.

Big files and browser memory

A 5-minute 4K H.264 video at 50 Mbps is ~1.9 GB — right at the WebAssembly memory ceiling. A 15-minute 4K master likely won't fit. For long 4K source files, split with our trim tool, downscale each part, then merge.

iPhone 4K, GoPro, Sony A7 — all work

iPhone 4K is HEVC by default. GoPro Hero 10+ is HEVC. Sony A7s III is XAVC HS (HEVC). All decode in browser. The output is always H.264 MP4 for universal compatibility — if you want an HEVC 1080p output instead, use our convert tool.

Privacy

Your 4K originals are usually big personal masters — vacations, family, professional shoots under NDA. Online downscalers upload them. Here, the file stays on your disk.

FAQ

What about 8K?

If your browser can read the file, we can downscale it. The decode is the bottleneck — an 8K source is a 4x larger memory footprint than 4K.

Will I lose detail?

Yes, by definition — you have a quarter the pixels. But at viewing distances under 6 feet from a 50" 4K TV, the eye won't resolve the difference anyway. For phones and laptops, 1080p is indistinguishable.

What's the output format?

MP4 with H.264 video, AAC audio. Plays everywhere.

How long does a 5-minute 4K downscale take?

5–10 minutes on a modern laptop. Phones are slower. The 4K decode is the slow part.

Can I downscale 4K 60fps to 1080p 30fps at the same time?

Not on this page, but the speed/framerate tool handles framerate conversion separately.

Does the file get uploaded anywhere?

No. Disconnect your internet after loading — downscaling still works.