ULID Generator

Generate ULIDs - Universally Unique Lexicographically Sortable Identifiers with timestamp and random components.

ULID Generator tool

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Example

Input: Paste 01ARZ3NDEKTSV4RRFFQ69G5FAV into the decoder

Result: Valid ULID - Timestamp: 1469922850259 - 2016-07-30T23:54:10.259Z

The first 10 characters of a ULID encode a millisecond Unix timestamp in Crockford Base32 and the last 16 are random. Generated ULIDs are new random values each time.

  1. Click "Generate 1" to create a single new ULID with a timestamp encoded from the current moment.
  2. To generate multiple ULIDs at once, enter a count from 1 to 100 in the Count field and click the "Generate" button showing that number.
  3. Review the decoded timestamp shown alongside each ULID to verify the embedded creation time.
  4. Click the copy button next to any ULID, or "Copy All" for the whole list, to use them as database keys or identifiers.
  5. Paste an existing ULID into the ULID Decoder to check that it is valid and see the date and time it was created.

ULID vs UUID: Sortable Unique IDs Explained

A ULID is a 128-bit unique ID, written as 26 characters like 01ARZ3NDEKTSV4RRFFQ69G5FAV, that sorts by the time it was made. This generator creates one ULID or up to 100 at a time. It shows the timestamp inside each one and decodes any ULID you paste in.

The first 10 characters hold the creation time, in milliseconds since 1970. The last 16 are random. Because the time comes first, sorting ULIDs as plain text also sorts them by age, which a random UUID v4 cannot do. That helps with database keys, log entries and event streams, where new rows can go at the end of an index instead of being scattered through it.

ULIDs use Crockford Base32, an alphabet of digits and capital letters that leaves out I, L, O and U so IDs are hard to misread. They are safe in URLs and shorter than the 36-character UUID format. This tool makes them monotonic. IDs created in the same millisecond still come out in order, because the random part is raised by one instead of drawn again. The random bits come from the secure random number generator in your browser.

The decoder checks that a pasted value has 26 valid characters and shows its timestamp as a number and as an ISO date. It accepts small letters, but not I, L, O or U. Keep in mind that anyone can read the creation time from a ULID, so do not use one where that time should stay private. For fully random IDs, use the UUID Generator. To turn a millisecond timestamp into a local date, try the Unix Timestamp Converter.

Sources

Frequently Asked Questions

Both are 128-bit IDs. A UUID v4 is 122 random bits written as 36 hex characters with hyphens, and it has no order. A ULID puts a 48-bit timestamp in front of 80 random bits and is written as 26 Base32 characters, so ULIDs sort by creation time. Use ULIDs when order matters and UUIDs when you need the standard format.
Yes. Both are 128 bits, so a ULID can be converted to the UUID layout and stored in a native UUID column. Many ULID libraries include that conversion. You can also store the 26-character text form in a CHAR(26) column, which is easy to read and still sorts by time.
Each ULID has 80 random bits, which gives about 1.2 trillion trillion possible values for every millisecond. That is fewer than the 122 random bits in a UUID v4, but a clash is still extremely unlikely in real systems. In this tool, IDs made in the same millisecond are also kept in order and unique.
UUID v7, defined in RFC 9562 in 2024, uses the same idea: a 48-bit millisecond timestamp followed by random bits. The difference is the format. A UUID v7 looks like any other UUID, so it fits existing UUID columns and tools. A ULID is shorter as text. Pick v7 for compatibility, or ULID for shorter strings.

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