MD5 Hash rfc 1321
Compute the 32-character hexadecimal MD5 digest of a string. Suitable for checksums, not for security.
What this tool does
MD5 turns input of any length into a fixed 128-bit value, normally written as 32 hexadecimal characters. The same input always produces the same digest, a single changed character produces a completely different digest, and the original cannot be derived from the result.
However, MD5 is broken with respect to collision resistance. Techniques for deliberately producing two different inputs with the same digest are well known and fast enough to run on ordinary hardware. That rules MD5 out for password storage, digital signatures, and integrity verification against a determined attacker.
It still appears in places where security is not the goal: cache keys, duplicate detection, quick corruption checks after a transfer, and compatibility with legacy systems that already store MD5 values.
When to use it
Use it when comparing against values a legacy system already stores, when checking quickly whether two files or strings are duplicates, when generating cache keys or temporary identifiers, or when verifying a published checksum for a download.
Input and output examples
hello
5d41402abc4b2a76b9719d911017c592
The same input produces the same digest in any environment.
Hello
8b1a9953c4611296a827abf8c47804d7
Changing only the first letter changes the entire digest.
empty string
d41d8cd98f00b204e9800998ecf8427e
Even empty input has a fixed-length digest. Seeing this value means the input was empty.
Notes and limitations
Storing passwords as MD5 is dangerous: digests of common passwords are catalogued in lookup tables, so the original is recovered by a simple search. Use bcrypt, scrypt, or Argon2, which are deliberately slow, for passwords. Choose SHA-256 or stronger when security matters, and HMAC when you need message authentication. Hashing is one-way, so this tool cannot turn an MD5 value back into the original text.
Frequently asked questions
Can an MD5 digest be reversed?
Not mathematically, because hashing is one-way. But common strings can be looked up in precomputed tables, so short or predictable values are effectively exposed.
Is MD5 still acceptable?
For non-security purposes such as cache keys, duplicate detection, and simple corruption checks, yes. For authentication, signatures, and password storage, no.