updated
Sep 26, 2026
632KB
file size
6.4K
downloads
Kvazaar is a free, open-source HEVC encoder from Ultra Video Group at Tampere University, a small command-line tool that turns raw video frames into compact H.265 streams, released under a BSD licence with no paid edition.
Kvazaar is the HEVC encoder that universities, researchers and developers reach for when they want clean, BSD-licensed code rather than a finished app.
It is a single command-line program that takes raw video frames in and writes a compressed H.265 stream out, and nothing more.
That narrowness is the whole point, and it is also the first thing to know before you download it.
What Kvazaar Actually Does - in Plain Terms
An encoder is the part of a converter that does the actual squeezing. Kvazaar does that squeezing for HEVC, the format also called H.265, and leaves every other job to other tools.
It is written and maintained by Ultra Video Group at Tampere University in Finland. The same team builds uvg266, its encoder for the newer H.266/VVC standard.
There is no window, no installer and no menu. If a command line is unfamiliar ground, the explainer on GUI versus command-line tools is a five-minute read that makes the rest of this page easier.
The catch nobody mentions:
Kvazaar only reads raw YUV or Y4M frames. Point it at an MP4 or MKV straight from your phone or camera and it will not decode it, so you need FFmpeg in front of it to unpack the video first.
What Is in the Download
The download page carries several builds of the same encoder, and they are not interchangeable. The official Windows files are plain ZIP archives: unpack them anywhere and run kvazaar.exe from a terminal.
| File | What it is | Pick it if |
|---|---|---|
| Kvazaar-2.3.2-win64-release.zip | Official 64-bit Windows build from Ultra Video Group | You are on any normal Windows 10 or 11 PC - this is the default choice |
| Kvazaar-2.3.2-win32-release.zip | Official 32-bit Windows build | You are stuck on a 32-bit copy of Windows |
| Kvazaar 2.3.2 builds compiled by Barough (.7z) | Unofficial community builds compiled with a recent version of the GCC compiler | You want the newest code and are happy to test an unofficial build |
| kvazaar_v2.3.1 build compiled by LigH (.7z) | An older community build from before 2.3.2 | You need to match results from an earlier project |
| kvazaar-2.3.2.tar.xz | Source code, not a ready-to-run program | You are on Linux and will compile it yourself |
There is no macOS build on the page. Mac users can install Kvazaar through Homebrew or compile it from the same source archive.
Your First Encode, Step by Step
The practical way to use Kvazaar on Windows is to let FFmpeg decode your video and pipe the raw frames straight in. Put both programs in the same folder, open a terminal there, and follow these steps.
- Encode the picture. Run ffmpeg -i input.mp4 -pix_fmt yuv420p -f yuv4mpegpipe - | kvazaar -i - --input-file-format y4m --preset medium -o video.hevc
- Check the result. You now have a bare H.265 stream with no sound and no container around it, which is normal.
- Put it back in a file players understand. Open video.hevc in MKVToolNix, add the original file for its audio track, and save an MKV.
- Set the frame rate when you mux. A bare HEVC stream does not carry a reliable frame rate, so enter your source's rate in MKVToolNix - a wrong value is the usual cause of sound drifting out of sync.
This pipeline is decoding, encoding and remuxing in a row. If those words blur together, the guide on decoding, encoding and transcoding sorts them out before a long encode rather than after.
Presets: the Dial Between Speed and Size
Kvazaar uses the same ten preset names as x264 and x265, from ultrafast to placebo, and medium is the default. Slower presets search harder and give smaller files at the same quality.
Quality is set with --qp, where lower numbers mean better quality and bigger files, or with --bitrate when you need to hit a target size. Test on a thirty-second clip first, because the right setting depends heavily on the source.
Threading is automatic, so Kvazaar spreads the work across your processor cores without any extra switches.
What Changed in 2.3.2
Version 2.3.2 was released on 17 September 2025 and is still the current stable release. It is a fixes release rather than a features one, but one change is worth knowing about.
- veryslow got better. Fixed cost calculations for asymmetric motion partitions mean AMP is now switched on in the veryslow preset - files come out roughly 3% smaller at the same quality, at about three quarters of the previous speed.
- 10-bit encoding fixes. Several bugs in 10-bit output were corrected.
- Y4M reading fixed. This matters directly for the FFmpeg pipe method above.
- Better rate control. Bitrate targeting was improved, and the default settings now match the medium preset exactly.
- Build fixes. Windows ARM64, Android and iOS builds work again for developers compiling their own.
The full list is in the Kvazaar 2.3.2 release notes on GitHub.
Kvazaar or x265?
For most people encoding their own videos, x265 is the better HEVC encoder, and it is the one built into almost every converter. Kvazaar earns its place for different reasons.
| Kvazaar | x265 | |
|---|---|---|
| Licence | BSD 3-clause - easy to embed in your own software, including closed-source | GPL, or a paid commercial licence |
| Input | Raw YUV and Y4M only | Raw YUV and Y4M, but usually used inside FFmpeg or a GUI that handles any file |
| Friendly front-ends | Very few | HandBrake, StaxRip, Shutter Encoder and many more |
| Pick it when | You are a developer, researcher or student who needs readable, permissively licensed code | You just want smaller video files that play everywhere |
Intel's SVT-HEVC used to be the third free option, but it is discontinued. Kvazaar and x265 are the two still under active development.
Who Should Look Elsewhere
The tell is simple: if the video you want to shrink ends in .mp4, .mov or .mkv and you would rather click a button than type a command, Kvazaar is the wrong tool.
- Want a window and presets? HandBrake encodes HEVC with x265 and opens nearly any file.
- Want full control with a GUI? StaxRip wraps x265 and other encoders in one pipeline.
- Need speed above all? NVEnc hands HEVC encoding to an NVIDIA graphics card and runs many times faster.
- Open to AV1 instead? SVT-AV1 is the practical free choice, and the guide on whether AV1 beats H.265 helps you decide.
For a side-by-side of the free options, see the guide to the best free HEVC encoders for Windows.
Playing What You Encode
VLC Media Player and MPC-BE play HEVC out of the box, with no extra codecs needed.
For the Windows Photos and Media Player apps, add Microsoft's HEVC Video Extensions from Device Manufacturer. The guide to the best players for HEVC files covers the rest.
Quick questions
Is Kvazaar free?
Yes, completely. It is open source under the BSD 3-clause licence, with no paid edition and no limits.
Can Kvazaar open MP4 or MKV files?
No. It reads only raw YUV and Y4M frames, so use FFmpeg to decode your file and pipe the frames in, as shown in the steps above.
Does Kvazaar have a graphical interface?
No, it is a command-line program only. If you want a window, HandBrake does HEVC encoding with x265 behind a normal interface.
Kvazaar or x265 - which is better?
For everyday encoding, x265, because almost every converter uses it and it is very well tuned. Kvazaar is the better fit when you need BSD-licensed code to build into your own software.
Does Kvazaar support 10-bit video?
Yes, and version 2.3.2 fixed several 10-bit bugs. 10-bit output needs a build compiled for it, so check the build notes before relying on it for HDR work.
Can I use Kvazaar inside FFmpeg?
Yes, if your FFmpeg build includes it, as the libkvazaar encoder. Many Windows builds of FFmpeg leave it out, so the pipe method on this page is the reliable route.
For more encoders and converters, browse the full video encoders category.
Download Kvazaar 2.3.2 and see how it handles your files, or tell us how you got on if you have used it before.
