Identifiers
Generate a fresh batch or inspect the readable fields of CUID and KSUID.
Choose an algorithm and settings below. Every explicit run creates a fresh batch; editing settings only marks the previous batch stale.
Processing stays in this browser. Inputs are not sent to a server.
Batch 1–1,000; NanoID length 1–128; CUID2 length 2–32. Custom alphabet: 2–64 distinct printable ASCII characters, without spaces. Decode input: at most 128,000 characters and 1,000 IDs.
Choose settings, then run.
Use the Nano ID generator when a database import, test fixture or short URL needs identifiers with specific character and length rules. Choose the format your receiving system expects before shortening the output.
The four modes do different jobs: NanoID offers a custom alphabet, CUID2 hides its internal inputs behind a hash, legacy CUID retains readable fields, and KSUID carries a seconds timestamp.
The Nano ID generator keeps four algorithms together while showing only their supported settings. A shorter NanoID is allowed; a shortened KSUID would lose its format, so its length stays fixed.
CUID and KSUID expose time-bearing structure. Their reports retain the encoded fields, while NanoID and CUID2 remain opaque. A parsed timestamp is a stored value, not proof of when an event happened.
NanoID starts at 21 URL-safe characters; CUID2 starts at 24 lowercase alphanumeric characters. Custom alphabets apply only to NanoID. Duplicate alphabet characters produce an error instead of extra weight.
Collision probability uses expected total issuance, separate from the batch count. For KSUID, enter the maximum number sharing a single timestamp second. Legacy CUID does not receive a misleading uniform-string estimate.
The preview begins with 50 records and expands by 100. Copy and downloads include all results. Decode rejects the whole batch if any non-empty line is invalid.
Choose URL-safe, hexadecimal, digits or your own alphabet. The official rejection sampler avoids the modulo bias that would otherwise favor some characters in a non-power-of-two alphabet.
CUID2 uses SHA3-512 to combine time, salt, a counter and a session fingerprint. It begins with a lowercase letter. Length can change from 2 to 32, but alphabet and internal fields are not editable.
The format has a c prefix, Base36 milliseconds, a four-character counter, a four-character fingerprint slot and eight random characters. This implementation fills the fingerprint slot with a random session marker instead of reading browser properties.
A KSUID encodes 20 bytes into 27 case-sensitive Base62 characters. Four bytes store a seconds offset from Unix 1400000000; the other sixteen bytes hold random payload. The decoder reports both UTC time and raw payload.
Yes. Choose Custom alphabet in NanoID mode and enter 2–64 unique visible ASCII characters. A duplicate, space or unsupported Unicode character is rejected. Other algorithms keep their defined alphabets.
Start with 21 when you do not have a tighter requirement. At 64 symbols that gives 126 ideal space bits. Shortening the string or using digits alone reduces the space exponentially; enter your total issuance to see the change.
CUID exposes milliseconds, a counter and a fingerprint slot. CUID2 hashes its internal inputs into an opaque string and is the replacement recommended by its authors. The old format is retained here for compatibility testing.
It puts an unsigned 32-bit seconds offset before 128 random payload bits. The epoch is Unix 1400000000. Decode mode returns that offset, Unix milliseconds, UTC text and payload; it cannot establish that the encoded time is truthful.
A short code cannot guarantee uniqueness across arbitrary issuance. With ten digits and six positions there are only one million outputs. Use a database constraint and retry policy, consider expiration, and estimate the population of simultaneously relevant codes before choosing a length.
Have a question about an ID?
Use the Nano ID generator to compare the format and collision assumptions, then export a fresh batch with the settings your application requires.