Developer Tools
GUID = UUID v4 — .NET calls it GUID, RFC calls it UUID. Choose by use-case, not name. Nothing stored on server, bulk, free.
v4 random → session IDs. v7 time-ordered → DB primary keys (no index fragmentation). ULID/NanoID → URL-safe.
Which ID should I use?
| Tool | Sortable? | URL-safe? | Size | Use when |
|---|---|---|---|---|
| UUID v4 / GUID | No | No | 36 chars | .NET Guid.NewGuid(), random PK, session IDs |
| UUID v7 | Yes (time) | No | 36 chars | Postgres/MySQL primary key — no index fragmentation |
| ULID | Yes | Yes | 26 chars | Frontend, sortable + URL-safe |
| NanoID | No | Yes | 21 chars | Short URLs, compact IDs |
Tip: For databases, v7 > v4. v4 random writes fragment clustered indexes. v7 is time-ordered.
UUID v4 Generator (GUID)
Generate secure, random UUID v4 — same as .NET GUID — in bulk.
Use when: Random IDs, C#, SQL Server NEWID(). Don't use: DB PK needing sort → use v7.
UUID v7 Generator
Time-ordered UUID v7 — 48-bit timestamp + random. Best for databases.
Use when: Postgres, MySQL, clustered index. Cuts storage 55% vs VARCHAR.
ULID Generator
Sortable, URL-safe ULIDs with timestamp + randomness.
Use when: Frontend IDs, logs — sortable and URL-safe.
NanoID Generator
Compact 21-char URL-friendly IDs, custom alphabet.
Use when: Short URLs, collision-sensitive but small.
UUID Validator
Validate format and version (v1, v4, v7, ULID).
UUID Decoder
Inspect version, variant, timestamp, and randomness.
GUID vs UUID?
Same thing. Microsoft called it GUID (Globally Unique Identifier) in .NET Guid.NewGuid(). RFC 9562 calls it UUID. A GUID is a UUID v4. If you need sortable DB keys, switch to UUID v7.