BLAKE3 hash
Compute a BLAKE3 digest of any file, on your device.
Runs on your device. The file is never uploaded.
BLAKE3 hash prints the 32 byte default output as 64 lowercase hex characters, matching what b3sum prints for the same bytes. Its chunk tree is what lets an implementation split the work over a file. Neither the extendable output length, the keyed mode nor the derive-key context is exposed, because only your bytes go in.
Questions
How long is a BLAKE3 digest here?
256 bits, or 64 lowercase hex characters. BLAKE3 has an extendable output and can produce any length you ask for, but this tool takes the hash-wasm default of 32 bytes and offers no length option. That default is also what b3sum prints, so the two line up without any configuration.
Will this match b3sum?
It should, for the same bytes. This tool passes no key and no derivation context, so it computes the plain unkeyed BLAKE3 hash at the default 32 byte length, which is what b3sum prints by default. If two values disagree, check that both sides hashed the identical file, trailing newline included.
Is BLAKE3 secure?
It is a cryptographic hash, the successor to BLAKE2, and it aims at the same properties as SHA-256 rather than the error detection that CRC32 and xxHash provide. Where compatibility matters more than anything, SHA-256 is still the most widely accepted choice.
Can I get a keyed hash or key derivation mode?
No. BLAKE3 defines keyed hashing and a key derivation mode, but this tool calls it with your file bytes only, passing neither a key nor a context string. For a keyed digest, use the HMAC tool, which takes a key and lets you pick MD5, SHA1, SHA256, SHA384 or SHA512.
Why is it fast on big files?
BLAKE3 uses a tree structure over chunks, which is what allows implementations to work on parts in parallel. What you get here is hash-wasm WebAssembly build, running in a Web Worker so a large file does not freeze the page.