UUID Lowercase
Paste any UUID (or multiple UUIDs) and convert to lowercase instantly. Normalizes UUIDs to the canonical RFC 4122 lowercase form expected by most databases and libraries.
UUID Lowercase
Powered byJavaScript & RFC 4122
All conversion happens locally in your browser. Nothing is sent to any server.
Paste UUIDs and click Convert to get lowercase versions.
Why is lowercase the canonical UUID form?
RFC 4122 states that UUID hex digits "should" be output in lowercase. Most programming languages (Node.js, Python, Go, Rust) and databases (PostgreSQL, MySQL, MongoDB) default to lowercase, making it the universally accepted canonical form for UUID interoperability.
Supports multiple UUIDs
Paste multiple UUIDs (one per line) and the tool converts each one independently in a single click.
Format preserved
Hyphens and UUID structure remain unchanged. Only the alphabetic hex characters are lowercased.
Common use cases
Normalizing UUIDs from Windows APIs, .NET GUIDs, or legacy systems that output uppercase hex to the RFC canonical lowercase form.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label standardized by the Internet Engineering Task Force under RFC 4122. Also known as a GUID in Microsoft ecosystems, UUIDs are designed to be globally unique without a central registry.
While UUIDs are technically case-insensitive, RFC 4122 recommends lowercase as the canonical output. Most modern databases and languages follow this convention.
- 128 bits = 16 bytes of data
- 36-character string: 32 hex digits + 4 hyphens
- RFC 4122 canonical form uses lowercase hex
- Case-insensitive for comparison purposes
UUID Format (Canonical Lowercase)
32 bits
16 bits
16 bits
16 bits
48 bits
RFC 4122 canonical form — all hex digits in lowercase, hyphens in standard positions.
UUID Versions Compared
There are several UUID versions — all output lowercase hex in their canonical form.
| Version | Generation Method | Best For | Requires |
|---|---|---|---|
| v1 | MAC address + timestamp | Time-ordered logging — UUID v1 Generator → | Network interface |
| v2 | DCE Security (POSIX UID/GID) | Legacy DCE systems | System identity |
| v3 | MD5 hash of namespace+name | Deterministic IDs from names — UUID v3 Generator → | Namespace UUID + input |
| v4 | Cryptographically random | General purpose — most common — UUID v4 Generator → | Nothing (random) |
| v5 | SHA-1 hash of namespace+name | Deterministic IDs (more secure than v3) | Namespace UUID + input |
| v6 | Reordered timestamp (RFC 9562) | Sortable time-based IDs | Clock + node |
| v7 | Unix timestamp + random (RFC 9562) | Database-friendly sortable IDs | Nothing (modern standard) |
Example UUIDs to Convert
Click an uppercase example UUID to convert it to lowercase instantly.
How This UUID Lowercase Tool Works
Each UUID is validated against the standard RFC 4122 pattern, then all alphabetic hex characters are converted to lowercase. The hyphenated structure remains completely intact.
Everything runs locally in your browser — no network requests, no storage, no tracking.
Common Use Cases
This tool is most useful when you need to:
Frequently Asked Questions
Concise answers to common questions about UUID lowercase conversion.
uuid.uuid4()), Node.js (crypto.randomUUID()), Go, and Rust all produce lowercase by default. Uppercase is technically valid but non-canonical.
550E8400-... and 550e8400-... represent the same UUID. However, string equality checks in certain languages or databases may treat them as different values unless case-insensitive comparison is used. Normalizing to lowercase prevents this ambiguity.
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