Generators

These tools produce values you need on demand rather than transforming something you already have: an identifier for a new record, a fingerprint of a file, a schedule for a recurring job.

What each one is for

The UUID Generator produces 128-bit identifiers that can be created independently on different machines without coordination and still not collide. Version 4 is random and the usual default. If you are using UUIDs as database primary keys, consider that their randomness fragments B-tree indexes, which is the problem time-ordered UUID v7 was designed to solve.

The Hash Generator produces a fixed-length fingerprint from any input. Output length is fixed by the algorithm, not the input — SHA-256 always returns 64 hexadecimal characters whether you hash one letter or a gigabyte.

The Cron Expression Generator builds the five-field schedule strings used by Unix cron and most job schedulers.

Two things that are easy to get wrong

Do not use a general-purpose hash for passwords. MD5, SHA-1 and SHA-256 are designed to be fast, which is exactly the wrong property for password storage — speed is what lets an attacker try billions of guesses per second. Passwords need a deliberately slow, salted algorithm: bcrypt, scrypt or Argon2id, with Argon2id the current recommendation. MD5 and SHA-1 are additionally broken for any security purpose, since practical collision attacks exist for both.

Cron treats day-of-month and day-of-week as OR, not AND. If you restrict both fields, most implementations run the job when either matches. 0 0 1 * 1 runs on the first of the month and also every Monday. Leave one field as * unless you genuinely want that behaviour.