ULID generator

What to do

Output

01M0R8RPE4R05FDQ1E2RKZTNMY
01M0R8RPE4AEVT4SCC1Q50MW32
01M0R8RPE4F01QVQCK71HHKQEG
01M0R8RPE4MDWD09TC7WYXYHGW
01M0R8RPE4M49Q3CKERZ4ZJKVJ
01M0R8RPE4FX3MAM4H33QKW619
01M0R8RPE4X2KZVTWTXH6S7BD6
01M0R8RPE4G76HRPB73EETZK3G
01M0R8RPE4QK1H7FJRW6CXBDJ0
01M0R8RPE467A4Y592ZYRKDENA

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Local · first 48 bits are the timestamp

Generates ULIDs — 26 characters of Crockford base32, with the first 48 bits being a millisecond timestamp, so a list of them sorts chronologically as plain text.

How to use the ulid generator

1 Paste your input. The result appears immediately.

2 Pick the operation you want.

3 Copy the result, or save it as a file.

That sortability is the entire reason to prefer a ULID over a UUID for a database key. A random v4 UUID as a primary key scatters inserts across a B-tree index, which fragments it and measurably hurts write throughput on a busy table; a ULID inserts at the end, keeping the index compact. It also means you can read the creation time out of the key, and sort by it without a separate column. The alphabet excludes I, L, O and U — the first three because they are confusable with 1 and 0, and U reportedly to avoid accidental obscenities.

Questions

Why is a ULID better than a UUID for a primary key? −

It sorts by time, so inserts land at the end of the index instead of scattering across it. That is a real write-throughput difference on a busy table.

How long is a ULID? +

Which letters are missing from the alphabet? +

Can I read the creation time from a ULID? +

Are ULIDs unique enough? +

Sources

ULID specification

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