What is an MD5 hash?

An MD5 hash is created by taking a string of an any length and encoding it into a 128-bit fingerprint. Encoding the same string using the MD5 algorithm will always result in the same 128-bit hash output. MD5 hashes are commonly used with smaller strings when storing passwords, credit card numbers or other sensitive data in databases such as the popular MySQL. This tool provides a quick and easy way to encode an MD5 hash from a simple string of up to 256 characters in length.

MD5 hashes are also used to ensure the data integrity of files. Because the MD5 hash algorithm always produces the same output for the same given input, users can compare a hash of the source file with a newly created hash of the destination file to check that it is intact and unmodified.

An MD5 hash is NOT encryption. It is simply a fingerprint of the given input. However, it is a one-way transaction and as such it is almost impossible to reverse engineer an MD5 hash to retrieve the original string.

Use Cases

Verifying File Integrity: MD5 can be used to verify the integrity of a file, ensuring that the file has not been tampered with during transmission or storage.
Password Storage: Although no longer recommended, in the past, some systems used MD5 to store user passwords in databases. It is now more advisable to use more secure hashing algorithms, such as bcrypt or Argon2.
Digital Signatures: In certain applications, MD5 might be used for digital signatures or generating checksums. However, for security-sensitive applications like digital signatures, more robust hash functions (such as SHA-256) are generally recommended.
Generating Unique Identifiers: MD5 can be used as a method for generating unique identifiers, although nowadays, it is more common to use longer hash values (such as SHA-256 or SHA-3).

Appendix

RFC: The MD5 Message-Digest Algorithm