Uniform Resource Locators (URL)
RFC 1738

Document Type RFC - Proposed Standard (December 1994; Errata)
Obsoleted by RFC 4266, RFC 4248
Last updated 2013-03-02
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Network Working Group                                     T. Berners-Lee
Request for Comments: 1738                                          CERN
Category: Standards Track                                    L. Masinter
                                                       Xerox Corporation
                                                             M. McCahill
                                                 University of Minnesota
                                                                 Editors
                                                           December 1994

                    Uniform Resource Locators (URL)

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.

Abstract

   This document specifies a Uniform Resource Locator (URL), the syntax
   and semantics of formalized information for location and access of
   resources via the Internet.

1. Introduction

   This document describes the syntax and semantics for a compact string
   representation for a resource available via the Internet.  These
   strings are called "Uniform Resource Locators" (URLs).

   The specification is derived from concepts introduced by the World-
   Wide Web global information initiative, whose use of such objects
   dates from 1990 and is described in "Universal Resource Identifiers
   in WWW", RFC 1630. The specification of URLs is designed to meet the
   requirements laid out in "Functional Requirements for Internet
   Resource Locators" [12].

   This document was written by the URI working group of the Internet
   Engineering Task Force.  Comments may be addressed to the editors, or
   to the URI-WG <uri@bunyip.com>. Discussions of the group are archived
   at <URL:http://www.acl.lanl.gov/URI/archive/uri-archive.index.html>

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RFC 1738            Uniform Resource Locators (URL)        December 1994

2. General URL Syntax

   Just as there are many different methods of access to resources,
   there are several schemes for describing the location of such
   resources.

   The generic syntax for URLs provides a framework for new schemes to
   be established using protocols other than those defined in this
   document.

   URLs are used to `locate' resources, by providing an abstract
   identification of the resource location.  Having located a resource,
   a system may perform a variety of operations on the resource, as
   might be characterized by such words as `access', `update',
   `replace', `find attributes'. In general, only the `access' method
   needs to be specified for any URL scheme.

2.1. The main parts of URLs

   A full BNF description of the URL syntax is given in Section 5.

   In general, URLs are written as follows:

       <scheme>:<scheme-specific-part>

   A URL contains the name of the scheme being used (<scheme>) followed
   by a colon and then a string (the <scheme-specific-part>) whose
   interpretation depends on the scheme.

   Scheme names consist of a sequence of characters. The lower case
   letters "a"--"z", digits, and the characters plus ("+"), period
   ("."), and hyphen ("-") are allowed. For resiliency, programs
   interpreting URLs should treat upper case letters as equivalent to
   lower case in scheme names (e.g., allow "HTTP" as well as "http").

2.2. URL Character Encoding Issues

   URLs are sequences of characters, i.e., letters, digits, and special
   characters. A URLs may be represented in a variety of ways: e.g., ink
   on paper, or a sequence of octets in a coded character set. The
   interpretation of a URL depends only on the identity of the
   characters used.

   In most URL schemes, the sequences of characters in different parts
   of a URL are used to represent sequences of octets used in Internet
   protocols. For example, in the ftp scheme, the host name, directory
   name and file names are such sequences of octets, represented by
   parts of the URL.  Within those parts, an octet may be represented by

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RFC 1738            Uniform Resource Locators (URL)        December 1994

   the chararacter which has that octet as its code within the US-ASCII
   [20] coded character set.

   In addition, octets may be encoded by a character triplet consisting
   of the character "%" followed by the two hexadecimal digits (from
   "0123456789ABCDEF") which forming the hexadecimal value of the octet.
   (The characters "abcdef" may also be used in hexadecimal encodings.)

   Octets must be encoded if they have no corresponding graphic
   character within the US-ASCII coded character set, if the use of the
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