Free UUID and ULID Generator

How this tool computes its result

Generates random identifiers using two algorithms. For UUID v4, it calls the native crypto.randomUUID() API and optionally formats the result as lowercase (default), UPPERCASE, or no-hyphen (removes all dashes). For ULID, it encodes the current timestamp into a 10-character time component (base32 alphabet "0123456789ABCDEFGHJKMNPQRSTVWXYZ", 32-bit increments per millisecond, highest precision), then appends 16 random base32 characters from crypto.getRandomValues(). Both algorithms can generate bulk IDs up to 500 at a time (capped in the UI), and the output displays all generated IDs stacked in a code block.

Worked example

Generating 3 UUIDs with default lowercase format produces three lines like "a5c3f1b2-9d2c-4e8f-b1a3-2c5d8e9f1a2b" (each from crypto.randomUUID()). Generating 3 ULIDs produces three lines like "01ARZ3NDEKTSV4RRFFQ69G5FAV" and "01ARZ3NDEKTSV4RRFFQ69G5G0H" (same time component "01ARZ3NDEKTSV" because they are generated within the same millisecond, different random tails). Switching the UUID format to "no-hyphen" converts a previously copied UUID to "a5c3f1b29d2c4e8fb1a32c5d8e9f1a2b".

When not to use this tool

These are not cryptographically signed or verifiable — UUIDs are random 128-bit values with no checksum or signature, so a malformed or truncated UUID is indistinguishable from a valid one. ULIDs include a timestamp, but that timestamp is set at generation time on the client, so if your system clock is wrong, the ULID's time component is also wrong.

Common mistakes

• - Generating a large batch (e.g., 500 IDs) and expecting them all to be unique across all future generations — they are highly likely to be unique within a single batch, but collision probability increases linearly with the total number generated across all sessions, especially for UUIDs where each is independently random.
• - Assuming the ULID timestamp encodes your server time — ULIDs are generated and time-stamped on the client (browser), so if there is a clock skew between client and server, the ULID's time component reflects the client's view.
• - Relying on UUIDs or ULIDs to be sequential — UUID v4 is random, so successive IDs have no ordering; ULID includes a timestamp, but the random suffix is still random, so ULIDs generated at slightly different times may not sort in expected order if the time difference is very small.

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