MD5 Hash Calculator

MD5 message digest of any text, returned as a 32 character hexadecimal string.

What it does

MD5 is a hash function defined in RFC 1321. It takes an input of any length and returns a fixed 128 bit value, usually written as 32 hexadecimal characters. The same text always produces the same digest, which is what makes it useful for checking that a file or message arrived unchanged.

The tool above hashes text in your browser and shows the digest, the digest length, and the input size. Nothing is sent anywhere, and the result appears as soon as you calculate. This is handy for confirming a checksum, testing an input against a known vector, or seeing how a small edit reshapes the whole digest.

Hashing differs from encryption in a key way. There is no key and no way back. You cannot recover the original text from a digest, so MD5 is a one way function. That property is what people rely on for integrity checks, where the goal is to compare two copies rather than to hide a secret.

MD5 was designed for speed, and that speed is now a weakness. Practical collisions have been demonstrated for years, meaning two different inputs can produce the same digest. RFC 6151 documents the attacks and states that MD5 must not be used where collision resistance matters, such as digital signatures or certificates.

Use MD5 for non security tasks like spotting a corrupted download, and reach for SHA-256 or a dedicated password function for anything that guards a secret. A fast general hash like MD5, or even a plain SHA, is a poor choice for passwords because attackers can try billions of guesses per second against a stolen database.

How to use

1. Type or paste the text you want to hash.
2. Keep it under 500 characters for this tool.
3. Press calculate to get the 32 character digest.
4. Compare the digest with the value you expected.
5. Edit one character and hash again to see the whole digest change.
6. Switch to a SHA calculator when the hash is protecting something sensitive.

Formula

Digest

128 bit result written as 32 hexadecimal characters.

Block

512 bits of padded input processed at a time.

Round

One of four rounds of sixteen operations, 64 in total.

The message is padded so its length is 56 modulo 64 bytes, then the original length in bits is appended, then each 64 byte block is mixed with the running state. The final state of four 32 bit words forms the digest. This page implements the algorithm from RFC 1321 directly.

Worked example

Reference table

Limits

• Covers up to 500 characters of text in this page.
• Hashes text, not binary files. Hash a file with a command line tool instead.
• Uses the standard MD5 for UTF-8 text.
• MD5 collisions are known, so the digest is not proof of authorship.

Common mistakes

• Using MD5 to store or check passwords.
• Trusting a digest alone as a signature without a secure channel.
• Assuming a matching digest proves a file is safe, when it only shows it matches.
• Comparing digests with mismatched case or stray spaces.
• Reaching for MD5 when SHA-256 costs almost nothing extra.

Try it yourself

Quick checks. Answers sit tucked under each question.

Questions

Sources

• IETF: RFC 1321, the MD5 message digest algorithm
• IETF: RFC 6151, updated security considerations for MD5

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