MD5 Hash Generator

What the MD5 generator does

This produces the MD5 hash of your text, a 32-character hex fingerprint. Type or paste your text, press Convert, and copy or download the result. MD5 is probably the most widely recognised hash there is, and it is useful to have to hand, but it carries an important warning that the sections below spell out: it is no longer safe for anything to do with security.

It runs in your browser, so nothing you enter is uploaded.

How to use it

1. Enter your text. Type or paste it, or upload a plain text file.
2. Press Convert. The 32-character MD5 hash appears, ready to Copy or Download.

What MD5 is

MD5 is a cryptographic hash function designed by Ronald Rivest in 1991, the fifth in his line of Message Digest algorithms, which is where the "MD" comes from. It takes any input and produces a 128-bit fingerprint, written as 32 hex characters, and for a long time it was the default hash almost everywhere, used to fingerprint files, store passwords, and back digital signatures. Like any hash it is deterministic, so the same text always gives the same result, and a single character changed gives a completely different one.

Why MD5 is broken

The reason for the warning is collisions, two different inputs that produce the same MD5 hash. A sound hash makes finding one effectively impossible. MD5 does not. Researchers found weaknesses through the 2000s until producing collisions became fast and routine, and this is not just a lab curiosity. In 2012 the Flame malware used an MD5 collision to forge a counterfeit Microsoft signing certificate, letting malicious code pose as a genuine Windows update. The body that studies these things, Carnegie Mellon's Software Engineering Institute, describes MD5 plainly as cryptographically broken and unsuitable for further use.

So MD5 must not be used for anything an attacker could target: not digital signatures, not certificates, not passwords, not verifying that a file has not been tampered with on purpose. For those, a modern hash like SHA-256 is the right choice. One point of nuance, the same one that applies to SHA-1: what broke is the resistance to crafted collisions, not the ability to hide an input, so MD5's fingerprints still reliably change when data changes by accident.

Where it is still fine to use

Broken for security does not make MD5 useless, and it is still everywhere for good reason. The collision attacks need someone deliberately crafting inputs. Where nobody is doing that, MD5 still works as a quick fingerprint. Checking that a download arrived intact, that a file was not corrupted in transit or storage, that two copies of something match, all of these are fine, because accidental corruption will not happen to produce a matching hash. It is also fast and produces a short, convenient fingerprint. The rule is the same as for SHA-1: if the question is "did this change by accident," MD5 is acceptable; if the question is "could someone have changed this on purpose," it is not.

No, you cannot decrypt an MD5 hash

This is the most common misunderstanding about MD5, so it is worth being clear. An MD5 hash cannot be turned back into the text it came from. It is one-way: it keeps only a fingerprint and throws the original away, so there is nothing to decrypt and no key involved. The many sites that advertise an "MD5 decrypter" are not reversing anything. They keep enormous lists of common words and leaked passwords, with the MD5 of each already worked out, and they simply look up whether your hash is on the list. If your input was a common word, they find it, because they had seen it before. If it was anything unusual, they cannot help. So MD5 still hides an input well, as long as that input was hard to guess, but its broken collision resistance means you should not lean on it for security regardless.

The library doing the work

The hashing is handled by js-md5, a small, widely used JavaScript implementation of MD5. Your text is read as bytes and run through the algorithm in your browser, with the 32-character hex result handed back.

Questions people ask

Is MD5 safe to use?

Not for anything security-related. It is broken against collision attacks, so it must not be used for signatures, certificates, passwords, or guarding against deliberate tampering. For non-security checks it still works.

Can I decrypt or reverse an MD5 hash?

No. MD5 is one-way, so the original text cannot be recovered. "MD5 decrypter" sites just look your hash up in lists of precomputed common inputs, which only works if the input was easy to guess.

Is it ok for file checksums?

Yes, for catching accidental corruption, such as confirming a download arrived intact. That is not an adversarial situation, so MD5's collision weakness does not come into play.

What should I use instead?

For anything where security matters, SHA-256 is the modern default. It is not affected by the attacks that broke MD5.

References

1. Rivest, R. (1992). RFC 1321: The MD5 Message-Digest Algorithm. Internet Engineering Task Force (IETF). https://www.rfc-editor.org/rfc/rfc1321
2. Turner, S., Chen, L. (2011). RFC 6151: Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms. Internet Engineering Task Force (IETF). https://www.rfc-editor.org/rfc/rfc6151
3. js-md5, an MD5 implementation for JavaScript (npm package). https://www.npmjs.com/package/js-md5