UUIDv7 Generator — Time-Ordered, Sortable UUIDs + Decoder

Real-world use cases

• Switch a Postgres primary key from v4 to v7

  You are designing a new table and want the ID column to also carry insertion order. Generate a handful of v7s here to eyeball the format, confirm they sort the way you expect, then set the column default to a v7 generator. New rows append near the right edge of the B-tree index instead of scattering, and "give me the 50 newest" becomes ORDER BY id DESC LIMIT 50 with no created_at column to maintain.

• Build an append-only event log or outbox table

  An outbox or event stream needs keys that are unique and keep events in the order they happened. Turn on monotonic mode and every v7 is strictly greater than the last, even when thousands land in the same millisecond. A consumer reads ORDER BY id and replays events in exactly the order the producer wrote them, with the timestamp readable straight off each ID.

• Find when a record was created straight from its ID

  A support ticket quotes a record ID like 0190b3b0-6400-7000-... and you need to know when it was created without touching the database. Paste it into the decoder and read the exact millisecond plus the UTC time. No schema access, no created_at lookup; the timestamp is baked into the first 48 bits of the ID itself.

• Seed test fixtures with realistic, time-ordered IDs

  Writing integration tests that assert ordering? Generate a batch of monotonic v7s, drop them into your fixtures, and assertions on "newest first" hold deterministically. Because they are standard UUIDs, they slot into any UUID column or ORM model without a custom type, and you can copy all and paste straight into a seed file.

Common pitfalls

• Treating a UUIDv7 as a secret. The random bits make collisions virtually impossible, but the leading 48 bits are a fully readable timestamp. A v7 is an identifier, not a token, so never use one as a session secret, password-reset code, or anything that must be unguessable in full.

• Exposing v7 IDs in public URLs without thinking about the leaked timing. Because the creation time decodes straight out, a public v7 reveals roughly when the record was made, and adjacent monotonic IDs hint at how fast you create records. If creation timing is sensitive, keep v7 internal and surface an opaque alias.

• Validating v7 with a generic UUID regex that ignores the version digit. A pattern that accepts any 8-4-4-4-12 hex will happily pass a v4 or a NIL UUID. Check that the 13th hex character is 7 and the variant bits are 0b10, which is exactly what the decoder on this page does before reading a timestamp.

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