Relevant Standards - Apache HTTP Server Version 2.4








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Apache HTTP Server Version 2.4



Apache > HTTP Server > Documentation > Version 2.4 > Miscellaneous DocumentationRelevant Standards


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    This page documents the relevant standards that the
    Apache HTTP Server implements or follows, along with brief
    descriptions.

    In addition to the information listed below, the following resources
    should be consulted:

    
      
        
        RFC Errata - Errata for published RFCs
      
      
        
        HTTP Working Group Specifications - A pre-compiled list
        of HTTP related RFCs and drafts
      
    

  
 HTTP
 URIs
 TLS/SSL
 Authentication
 Content Negotiation and Compression
 Proxying and Forwarding
 WebSocket
 CGI
 WebDAV
 Language/Country Codes



HTTP ¶

    Regardless of what modules are compiled and used, Apache as a
    basic web server complies with the following IETF standards:

    
      RFC 9110
      (Standards Track) - HTTP Semantics

      Defines the semantics shared by all versions of HTTP:
      methods, status codes, header and trailer fields, content
      negotiation, and message metadata. Obsoletes RFC 7231, 7232,
      7233, 7235, and 7694.

      RFC 9111
      (Standards Track) - HTTP Caching

      Defines HTTP caches and the associated header fields that
      control cache behavior or indicate cacheable response messages.
      Obsoletes RFC 7234.

      RFC 9112
      (Standards Track) - HTTP/1.1

      Defines the HTTP/1.1 message syntax and connection management.
      Obsoletes RFC 7230.

      RFC 9113
      (Standards Track) - HTTP/2

      Defines an optimized expression of HTTP semantics using
      binary framing and multiplexed streams over a single TCP
      connection. Obsoletes RFC 7540 and 8740.

      RFC 9114
      (Standards Track) - HTTP/3

      Defines the mapping of HTTP semantics over QUIC, providing
      similar features to HTTP/2 with reduced latency.

      RFC 1945
      (Informational) - HTTP/1.0

      The original HTTP/1.0 specification. Retained for historical
      reference; httpd still accepts HTTP/1.0 requests.
    

  

URIs ¶

    
      RFC 3986
      (Standards Track) - Uniform Resource Identifier (URI): Generic Syntax

      The generic syntax and resolution rules for Uniform Resource
      Identifiers. Obsoletes RFC 2396.

      RFC 6570
      (Standards Track) - URI Template

      Defines a compact sequence of characters for describing a
      range of URIs through variable expansion.
    

  

TLS/SSL ¶

    The following standards apply when mod_ssl is
    enabled:

    
      RFC 8446
      (Standards Track) - TLS 1.3

      The current version of the Transport Layer Security protocol,
      providing communications privacy over the Internet. Obsoletes
      RFC 5246 (TLS 1.2 specification text).

      RFC 5246
      (Standards Track) - TLS 1.2

      The previous widely-deployed version of TLS.  Still supported
      by httpd for compatibility with older clients.

      RFC 6960
      (Standards Track) - OCSP

      The Online Certificate Status Protocol, used for checking
      certificate revocation status in real time (OCSP stapling via
      SSLStaplingCache).

      RFC 6066
      (Standards Track) - TLS Extensions

      Defines TLS extensions including Server Name Indication (SNI),
      which httpd uses for name-based virtual hosting over TLS.
    

  

Authentication ¶

    Concerning the different methods of authentication:

    
      RFC 7617
      (Standards Track) - The 'Basic' HTTP Authentication Scheme

      HTTP Basic authentication, transmitting credentials as
      user-id/password pairs encoded in Base64. Obsoletes RFC 2617
      (Basic auth portion).

      RFC 7616
      (Standards Track) - HTTP Digest Access Authentication

      HTTP Digest authentication, providing a challenge-response
      mechanism that avoids sending the password in cleartext.
      Obsoletes RFC 2617 (Digest auth portion).
    

  

Content Negotiation and Compression ¶

    
      RFC 9110 - Content Negotiation

      Proactive and reactive content negotiation, including the
      Accept, Accept-Language, Accept-Encoding, and Accept-Charset
      header fields.

      RFC 7932
      (Informational) - Brotli Compressed Data Format

      Defines the Brotli compression algorithm, supported via
      mod_brotli.
    

  

Proxying and Forwarding ¶

    When mod_proxy is enabled:

    
      RFC 7239
      (Standards Track) - Forwarded HTTP Extension

      Defines the Forwarded header field for conveying information
      about the client-facing side of proxy servers.

      RFC 9209
      (Standards Track) - The Proxy-Status HTTP Response Header Field

      Defines a mechanism for proxies to communicate the details
      of intermediary handling to the client.

      RFC 9220
      (Standards Track) - Bootstrapping WebSockets with HTTP/2

      Defines a mechanism for running the WebSocket protocol over
      a single HTTP/2 stream.
    

  

WebSocket ¶

    
      RFC 6455
      (Standards Track) - The WebSocket Protocol

      Defines the WebSocket protocol, enabling two-way
      communication between a client and server over a single TCP
      connection. Supported via mod_proxy_wstunnel.
    

  

CGI ¶

    
      RFC 3875
      (Informational) - The Common Gateway Interface (CGI) Version 1.1

      Defines the Common Gateway Interface for running external
      programs on a web server. Implemented by
      mod_cgi and mod_cgid.
    

  

WebDAV ¶

    When mod_dav is enabled:

    
      RFC 4918
      (Standards Track) - HTTP Extensions for Web Distributed Authoring
      and Versioning (WebDAV)

      Defines extensions to HTTP for distributed authoring
      operations. Obsoletes RFC 2518.

      RFC 3744
      (Standards Track) - Web Distributed Authoring and Versioning (WebDAV)
      Access Control Protocol

      Defines access control extensions to WebDAV.
    

  

Language/Country Codes ¶

    Language and country codes used in content negotiation:

    
      ISO 639-2

      ISO 639 provides two sets of language codes, one as a two-letter
      code set (639-1) and another as a three-letter code set (this part
      of ISO 639) for the representation of names of languages.

      
      ISO 3166-1

      Country names and corresponding alpha-2 and alpha-3 code
      elements.

      RFC 5646
      (Best Current Practice) - Tags for Identifying Languages

      Describes the structure and registry of language tags used in
      HTTP content negotiation (Accept-Language, Content-Language).
      Obsoletes RFC 3066.

      RFC 3282
      (Standards Track)

      Defines the Content-Language and Accept-Language header fields
      for indicating language preferences in HTTP messages.
    

  

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