Network Working Group T. Berners-Lee
Request for Comments: 3986 W3C/MIT
STD: 66 R. Fielding
Updates: 1738 Day Software
Obsoletes: 2732, 2396, 1808 L. Masinter
Category: Standards Track Adobe Systems
January 2005
Uniform Resource Identifier (URI): Generic Syntax
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
A Uniform Resource Identifier (URI) is a compact sequence of
characters that identifies an abstract or physical resource. This
specification defines the generic URI syntax and a process for
resolving URI references that might be in relative form, along with
guidelines and security considerations for the use of URIs on the
Internet. The URI syntax defines a grammar that is a superset of all
valid URIs, allowing an implementation to parse the common components
of a URI reference without knowing the scheme-specific requirements
of every possible identifier. This specification does not define a
generative grammar for URIs; that task is performed by the individual
specifications of each URI scheme.
Berners-Lee, et al. Standards Track [Page 1]
RFC 3986 URI Generic Syntax January 2005
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Overview of URIs . . . . . . . . . . . . . . . . . . . . 4
1.1.1. Generic Syntax . . . . . . . . . . . . . . . . . 6
1.1.2. Examples . . . . . . . . . . . . . . . . . . . . 7
1.1.3. URI, URL, and URN . . . . . . . . . . . . . . . 7
1.2. Design Considerations . . . . . . . . . . . . . . . . . 8
1.2.1. Transcription . . . . . . . . . . . . . . . . . 8
1.2.2. Separating Identification from Interaction . . . 9
1.2.3. Hierarchical Identifiers . . . . . . . . . . . . 10
1.3. Syntax Notation . . . . . . . . . . . . . . . . . . . . 11
2. Characters . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1. Percent-Encoding . . . . . . . . . . . . . . . . . . . . 12
2.2. Reserved Characters . . . . . . . . . . . . . . . . . . 12
2.3. Unreserved Characters . . . . . . . . . . . . . . . . . 13
2.4. When to Encode or Decode . . . . . . . . . . . . . . . . 14
2.5. Identifying Data . . . . . . . . . . . . . . . . . . . . 14
3. Syntax Components . . . . . . . . . . . . . . . . . . . . . . 16
3.1. Scheme . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2. Authority . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.1. User Information . . . . . . . . . . . . . . . . 18
3.2.2. Host . . . . . . . . . . . . . . . . . . . . . . 18
3.2.3. Port . . . . . . . . . . . . . . . . . . . . . . 22
3.3. Path . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.4. Query . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.5. Fragment . . . . . . . . . . . . . . . . . . . . . . . . 24
4. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.1. URI Reference . . . . . . . . . . . . . . . . . . . . . 25
4.2. Relative Reference . . . . . . . . . . . . . . . . . . . 26
4.3. Absolute URI . . . . . . . . . . . . . . . . . . . . . . 27
4.4. Same-Document Reference . . . . . . . . . . . . . . . . 27
4.5. Suffix Reference . . . . . . . . . . . . . . . . . . . . 27
5. Reference Resolution . . . . . . . . . . . . . . . . . . . . . 28
5.1. Establishing a Base URI . . . . . . . . . . . . . . . . 28
5.1.1. Base URI Embedded in Content . . . . . . . . . . 29
5.1.2. Base URI from the Encapsulating Entity . . . . . 29
5.1.3. Base URI from the Retrieval URI . . . . . . . . 30
5.1.4. Default Base URI . . . . . . . . . . . . . . . . 30
5.2. Relative Resolution . . . . . . . . . . . . . . . . . . 30
5.2.1. Pre-parse the Base URI . . . . . . . . . . . . . 31
5.2.2. Transform References . . . . . . . . . . . . . . 31
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