Hashes/Crypto
Argon2 Hash + Verify
Hash passwords with Argon2 (winner of the Password Hashing Competition, RFC 9106) — d/i/id variants, with verification against an existing hash.
Argon2 is the Password Hashing Competition winner and the algorithm recommended in RFC 9106 for hashing passwords. Unlike bcrypt, it deliberately demands a lot of memory, not just CPU time, which makes attacks on specialized hardware (GPUs, ASICs) much harder.
How to use it
- Hash: enter a password, pick a variant (Argon2d, Argon2i, or Argon2id), and set the parameters (memory, iterations, parallelism) to get a hash.
- Verify: paste a password and an existing Argon2 hash to check whether they match, without hashing manually yourself.
- Argon2id is the recommended default for most applications — it combines the strengths of Argon2i and Argon2d.
Common uses
- Checking that a backend generates correct Argon2 hashes with the expected parameters before a release.
- Tuning memory and iteration parameters to fit within a server's response-time budget (typically 250-500ms).
- Comparing Argon2 against bcrypt or PBKDF2 when choosing an algorithm for a new project.
Things to keep in mind
The memory parameter is Argon2's main defense: the more memory hashing requires, the more expensive it is for an attacker to parallelize an attack on a GPU with limited fast memory per chip.
Argon2id is recommended for most cases: Argon2i resists side-channel attacks better, Argon2d resists GPU attacks better, and id combines both approaches.
Article about this tool: Argon2: why this algorithm won the password hashing competition
Frequently asked questions
Why is Argon2 recommended over older hashing like MD5 or SHA-256 for passwords?
Argon2 is deliberately slow and memory-hard, making brute-force and GPU/ASIC-based cracking far more expensive, unlike fast general-purpose hashes like MD5 or SHA-256 which are unsuited for password storage.
What do the memory, iterations, and parallelism parameters control?
Memory cost sets how much RAM each hash attempt requires, iterations control how many passes are run, and parallelism sets the number of threads — increasing any of them raises the cost of cracking at the expense of slower hashing.
Which Argon2 variant should I use — d, i, or id?
Argon2id is the recommended default for password hashing, since it combines Argon2i's resistance to side-channel attacks with Argon2d's resistance to GPU cracking.
Where did Argon2 come from as a standard?
Argon2 won the 2015 Password Hashing Competition — an open contest among cryptographers aimed at finding the best algorithm for password hashing. OWASP has recommended it as the priority choice over bcrypt ever since.
Does the parallelism parameter only speed up hashing?
No, the same parameter equally speeds up brute-forcing for an attacker with multi-core hardware, so parallelism should be tuned to the server's actual core count rather than increased without reason.