Hashes, UUIDs, and When Each One Fits
Hashes and UUIDs can both look like opaque strings, but they answer different questions. Choosing between them becomes straightforward once you decide whether you need an identifier, a deterministic fingerprint, or a security control.
Use UUIDs to identify things
A UUID is generally generated to identify a record, request, or event. It is not derived from the content it identifies, so changing a record does not change its ID. UUIDs are useful for client-side placeholders, correlation IDs, and distributed systems where a central sequence is inconvenient.
Use hashes to compare exact input
A cryptographic hash produces a deterministic digest: the same bytes produce the same output. That makes SHA-256 useful for integrity checks and detecting changes. Whitespace, encoding, and line endings are part of the input, so two visually similar strings can have different hashes.
MD5 is appropriate only when a legacy integration requires it or for non-security compatibility checks. It should not be used for passwords, signatures, or new security-sensitive features.
Neither is a password strategy by itself
Do not store passwords as plain SHA-256 or MD5. Password storage needs a dedicated, slow password-hashing function with a unique salt and current security parameters. A generated password can be strong, but storage and verification still need to be designed separately.