RFC 4122 · PROPOSED STANDARD · 2005

A Universally Unique IDentifier URN Namespace

Overview

RFC 4122, “A Universally Unique IDentifier URN Namespace”, is a Proposed Standard document published in July 2005 by P. Leach, M. Mealling, R. Salz. It has been obsoleted by RFC 9562 — refer to the newer document for the authoritative version. The canonical text is published by the RFC Editor.

Abstract

This specification defines a Uniform Resource Name namespace for UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally Unique IDentifier). A UUID is 128 bits long, and can guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System and later in the Open Software Foundation\'s (OSF) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms.

This specification is derived from the DCE specification with the kind permission of the OSF (now known as The Open Group). Information from earlier versions of the DCE specification have been incorporated into this document. [STANDARDS-TRACK]

Abstract as published in the RFC, via rfc-editor.org.

What “Proposed Standard” means

An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.

Read this RFC

The canonical text of RFC 4122 is hosted at rfc-editor.org. Available in TXT,HTML.

Relationships to other RFCs
Obsoleted by
RFC 9562
Other RFCs from 2005

Who Is Online

In total there are 64 users online: 0 registered, 57 guests and 7 bots.

Most users ever online was 9,867 on 30 Jul 2026, 2:30 am.

Bots: AhrefsBot Baiduspider Bingbot Other Bot Other Crawler PetalBot SemrushBot

Users active in the past 15 minutes. Total registered members: 372