Command-line implementation of the BLAKE3 cryptographic hash function. Prints the BLAKE3 hashes of files or of standard input.
BLAKE3 is a cryptographic hash function that is:
Much faster than MD5, SHA-1, SHA-2, SHA-3, and BLAKE2.
Secure, unlike MD5 and SHA-1. And secure against length extension, unlike SHA-2.
Highly parallelizable across any number of threads and SIMD lanes, because it's a Merkle tree on the inside.
Capable of verified streaming and incremental updates, again because it's a Merkle tree.
A PRF, MAC, KDF, and XOF, as well as a regular hash.
One algorithm with no variants, which is fast on x86-64 and also on smaller architectures.
BLAKE3 is based on an optimized instance of the established hash function BLAKE2 and on the original Bao tree mode. The specifications and design rationale are available in the BLAKE3 paper. The default output size is 256 bits. The current version of Bao implements verified streaming with BLAKE3.
What's new in 1.8.7
version 1.8.7 Changes since 1.8.6: - Remove the arrayref dependency. Unfortunately the crates.io owner was compromised.
version 1.8.6 Changes since 1.8.5: - update_mmap and update_mmap_rayon (and by extension b3sum) now use seek rather than metadata to get the length of a file/mapping, and they tolerate mmap failures. That means b3sum will now memory map e.g. Linux block devices, which support mapping despite reporting length 0 in metadata. Hashing NUL files on Windows also works now, where previously it was an error unless you used --no-mmap or <. This change was originally proposed by @nabijaczleweli.
1.8.5Apr 25, 2026
Changes since 1.8.4: - Forcibly disable LTO when compiling C intrinsics from the Rust build. This fixes a build break on Arch Linux ARM: #550
Frequently asked questions
Is b3sum free?
Yes. b3sum is free and open-source software released under the CC0-1.0 OR Apache-2.0 OR (Apache-2.0 WITH LLVM-exception) license.
What is the latest version of b3sum?
The latest version is 1.8.7, released on Aug 20, 2026.
Is it safe to download b3sum?
The download button links to the official installer published on github.com, the same file Windows Package Manager installs. You can verify the downloaded file by comparing its SHA-256 checksum with fce0c2406a1e92b49fedd02a48a67dc5ba71c3a85eb80a2f950ed985f90e76e2.
Which Windows versions does b3sum support?
b3sum runs on Windows and is available for 64-bit (x64) systems.
How do I uninstall b3sum?
Open Settings › Apps › Installed apps, find b3sum and select Uninstall. From the command line, run winget uninstall --id=BLAKE3-Team.b3sum -e.
Is there a portable version of b3sum?
Yes. b3sum is available as a portable program (b3sum_windows_x64_bin.exe, 64-bit (x64)) that runs without installation. Copy it to any folder or USB drive and run it from there.
Alternatives to b3sum
Other Command Line Tools programs for Windows from different developers.
The Azure command-line interface (Azure CLI) is a set of commands used to create and manage Azure resources. The Azure CLI is available across Azure services and is designed to get you working quickly
