CUID generator — cuid2-style IDs that start with a letter

How to use the CUID generator

1. Set the Length, from 2 to 32 characters. The default of 24 matches cuid2’s default.
2. Set How many IDs, from 1 to 500.
3. Press Generate and copy the list.

What it does and when to use it

cuid2 is a popular choice for database primary keys and public record IDs in JavaScript projects. They are a good fit when you want IDs that are hard to guess, safe to show in URLs, free of upper case (so they survive case-insensitive systems) and never start with a digit.

Use this page to create IDs for seed data and fixtures, to test that your validation accepts the format, or to see how a shorter length looks. If you want time-sortable IDs, the ULID generator or the UUID generator with version 7 is a better match. For a plain random ID with a collision estimate on screen, try the Nano ID generator.

How it works

For each ID the tool:

1. Picks a random lowercase letter for the first character.
2. Builds an input string from the current time in base 36, a fresh random base-36 string as long as the ID, a counter that starts at a random value and goes up by one per ID, and a 32-character random fingerprint shared by the batch.
3. Hashes that string with SHA3-512, writes the hash in base 36, and keeps enough characters to reach the chosen length.

All random parts come from crypto.getRandomValues. The length sets an upper limit on strength: with 36 possible characters, a 24-character ID can hold at most about 124 bits, and a 10-character ID at most about 51 bits.

Worked examples

• Default length. Length 24 gives IDs such as z8m01lopqq86ngxsv40o60np and at3srcofghtnf9q6ky0giof2, followed by the note “Built like cuid2 … Not byte-compatible with any one library.”
• Short IDs. Length 10 gives values such as wauuslt5xg. That is handy for a demo, but at about 51 bits it is too short for a large table.

Limits and tips

• Lengths under about 16 raise the risk of duplicates in big datasets. Keep a unique index on the column either way.
• IDs are lowercase only. Do not upper-case them later, or they will no longer match.
• A cuid is an identifier, not a secret. Do not use one as a password or an API key.