Hypertext Transfer Protocol (HTTP) Field Name Registry

Created

  • 2021-10-01

Last Updated

  • 2026-10-09

Available Formats

Hypertext Transfer Protocol (HTTP) Field Name Registry

Registration Procedure(s)

  • Specification Required for Permanent registrations, Expert Review for Provisional registrations.

Expert(s)

  • Mark Nottingham, Roy Fielding

Reference

Note

See Section 16.3 of RFC 9110 for more information on defining and registering new HTTP Fields.

Note

New field names, along with changes to existing ones, can be requested using the registry interface or the mailing list defined in RFC 9110.

Note

The "Structured Type" column indicates the type of the field (per RFC 9651), if any, and may be "Dictionary", "List", or "Item".

Note that field names beginning with characters other than ALPHA or "*" will not be able to be represented as a Structured Fields Token and therefore may be incompatible with being mapped into field values that refer to it.

Available Formats

Field Name Status Structured Type Reference Comments
A-IM permanent RFC 3229: Delta encoding in HTTP
Accept permanent RFC 9110, Section 12.5.1: HTTP Semantics
Accept-Additions permanent RFC 2324: Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)
Accept-CH permanent List RFC 8942, Section 3.1: HTTP Client Hints
Accept-Charset deprecated RFC 9110, Section 12.5.2: HTTP Semantics
Accept-Datetime permanent RFC 7089: HTTP Framework for Time-Based Access to Resource States -- Memento
Accept-Encoding permanent RFC 9110, Section 12.5.3: HTTP Semantics
Accept-Features permanent RFC 2295: Transparent Content Negotiation in HTTP
Accept-Language permanent RFC 9110, Section 12.5.4: HTTP Semantics
Accept-Patch permanent RFC 5789: PATCH Method for HTTP
Accept-Post permanent Linked Data Platform 1.0
Accept-Query permanent List RFC 10008, Section 3: The HTTP QUERY Method
Accept-Ranges permanent RFC 9110, Section 14.3: HTTP Semantics
Accept-Signature permanent RFC 9421, Section 5.1: HTTP Message Signatures
Access-Control obsoleted Access Control for Cross-site Requests
Access-Control-Allow-Credentials permanent Fetch
Access-Control-Allow-Headers permanent Fetch
Access-Control-Allow-Methods permanent Fetch
Access-Control-Allow-Origin permanent Fetch
Access-Control-Expose-Headers permanent Fetch
Access-Control-Max-Age permanent Fetch
Access-Control-Request-Headers permanent Fetch
Access-Control-Request-Method permanent Fetch
Activate-Storage-Access provisional Item https://privacycg.github.io/storage-access-headers
Age permanent RFC 9111, Section 5.1: HTTP Caching
Allow permanent RFC 9110, Section 10.2.1: HTTP Semantics
ALPN permanent RFC 7639, Section 2: The ALPN HTTP Header Field
Alt-Svc permanent RFC 7838: HTTP Alternative Services
Alt-Used permanent RFC 7838: HTTP Alternative Services
Alternates permanent RFC 2295: Transparent Content Negotiation in HTTP
AMP-Cache-Transform provisional AMP-Cache-Transform HTTP request header
Apply-To-Redirect-Ref permanent RFC 4437: Web Distributed Authoring and Versioning (WebDAV) Redirect Reference Resources
Authentication-Control permanent RFC 8053, Section 4: HTTP Authentication Extensions for Interactive Clients
Authentication-Info permanent RFC 9110, Section 11.6.3: HTTP Semantics
Authorization permanent RFC 9110, Section 11.6.2: HTTP Semantics
Available-Dictionary permanent Item RFC 9842, Section 2.2: Compression Dictionary Transport
C-Ext obsoleted RFC 2774: An HTTP Extension Framework Status change of HTTP experiments to Historic
C-Man obsoleted RFC 2774: An HTTP Extension Framework Status change of HTTP experiments to Historic
C-Opt obsoleted RFC 2774: An HTTP Extension Framework Status change of HTTP experiments to Historic
C-PEP obsoleted PEP - an Extension Mechanism for HTTP Status change of HTTP experiments to Historic
C-PEP-Info deprecated PEP - an Extension Mechanism for HTTP Status change of HTTP experiments to Historic
Cache-Control permanent RFC 9111, Section 5.2: HTTP Caching
Cache-Group-Invalidation permanent List RFC 9875: HTTP Cache Groups
Cache-Groups permanent List RFC 9875: HTTP Cache Groups
Cache-Status permanent List RFC 9211: The Cache-Status HTTP Response Header Field
Cal-Managed-ID permanent RFC 8607, Section 5.1: Calendaring Extensions to WebDAV (CalDAV): Managed Attachments
CalDAV-Timezones permanent RFC 7809, Section 7.1: Calendaring Extensions to WebDAV (CalDAV): Time Zones by Reference
Capsule-Protocol permanent Item RFC 9297: HTTP Datagrams and the Capsule Protocol
CDN-Cache-Control permanent Dictionary RFC 9213: Targeted HTTP Cache Control Cache directives targeted at content delivery networks
CDN-Loop permanent RFC 8586: Loop Detection in Content Delivery Networks (CDNs)
Cert-Not-After permanent RFC 8739, Section 3.3: Support for Short-Term, Automatically Renewed (STAR) Certificates in the Automated Certificate Management Environment (ACME)
Cert-Not-Before permanent RFC 8739, Section 3.3: Support for Short-Term, Automatically Renewed (STAR) Certificates in the Automated Certificate Management Environment (ACME)
Clear-Site-Data permanent Clear Site Data
Client-Cert permanent Item RFC 9440, Section 2: Client-Cert HTTP Header Field
Client-Cert-Chain permanent List RFC 9440, Section 2: Client-Cert HTTP Header Field
Close permanent RFC 9112, Section 9.6: HTTP/1.1 (reserved)
CMCD-Object provisional Consumer Technology Association; CTA-5004 Common Media Client Data
CMCD-Request provisional Consumer Technology Association; CTA-5004 Common Media Client Data
CMCD-Session provisional Consumer Technology Association; CTA-5004 Common Media Client Data
CMCD-Status provisional Consumer Technology Association; CTA-5004 Common Media Client Data
CMSD-Dynamic provisional Consumer Technology Association; CTA-5006 Common Media Server Data (CMSD)
CMSD-Static provisional Consumer Technology Association; CTA-5006 Common Media Server Data (CMSD)
Concealed-Auth-Export permanent Item RFC 9729: The Concealed HTTP Authentication Scheme
Configuration-Context provisional OSLC Configuration Management Version 1.0. Part 3: Configuration Specification
Connect-UDP-Bind permanent Item RFC-ietf-masque-connect-udp-listen-16: Proxying Bound UDP in HTTP
Connection permanent RFC 9110, Section 7.6.1: HTTP Semantics
Content-Base obsoleted RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1 Obsoleted by RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1
Content-Digest permanent Dictionary RFC 9530, Section 2: Digest Fields
Content-Disposition permanent RFC 6266: Use of the Content-Disposition Header Field in the Hypertext Transfer Protocol (HTTP)
Content-Encoding permanent RFC 9110, Section 8.4: HTTP Semantics
Content-ID deprecated The HTTP Distribution and Replication Protocol
Content-Language permanent RFC 9110, Section 8.5: HTTP Semantics
Content-Length permanent RFC 9110, Section 8.6: HTTP Semantics
Content-Location permanent RFC 9110, Section 8.7: HTTP Semantics
Content-MD5 obsoleted RFC 2616, Section 14.15: Hypertext Transfer Protocol -- HTTP/1.1 Obsoleted by RFC 7231, Appendix B: Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
Content-Range permanent RFC 9110, Section 14.4: HTTP Semantics
Content-Script-Type obsoleted HTML 4.01 Specification
Content-Security-Policy permanent Content Security Policy Level 3
Content-Security-Policy-Report-Only permanent Content Security Policy Level 3
Content-Style-Type obsoleted HTML 4.01 Specification
Content-Type permanent RFC 9110, Section 8.3: HTTP Semantics
Content-Version obsoleted RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1
Cookie permanent RFC-ietf-httpbis-rfc6265bis-22, Section 5.8.1: Cookies: HTTP State Management Mechanism
Cookie2 obsoleted RFC 2965: HTTP State Management Mechanism Obsoleted by RFC 6265: HTTP State Management Mechanism
Cross-Origin-Embedder-Policy permanent Item HTML
Cross-Origin-Embedder-Policy-Report-Only permanent Item HTML
Cross-Origin-Opener-Policy permanent Item HTML
Cross-Origin-Opener-Policy-Report-Only permanent Item HTML
Cross-Origin-Resource-Policy permanent Fetch
CTA-Common-Access-Token provisional Consumer Technology Association; Chris Lemmons
DASL permanent RFC 5323: Web Distributed Authoring and Versioning (WebDAV) SEARCH
Date permanent RFC 9110, Section 6.6.1: HTTP Semantics
DAV permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
Default-Style obsoleted HTML 4.01 Specification
Delta-Base permanent RFC 3229: Delta encoding in HTTP
Deprecation permanent Item RFC 9745, Section 2: The Deprecation HTTP Response Header Field
Depth permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
Derived-From obsoleted RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1
Destination permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
Detached-JWS permanent RFC 9635: Grant Negotiation and Authorization Protocol (GNAP)
Differential-ID deprecated The HTTP Distribution and Replication Protocol
Dictionary-ID permanent Item RFC 9842, Section 2.3: Compression Dictionary Transport
Digest obsoleted RFC 3230: Instance Digests in HTTP Obsoleted by RFC 9530, Section 1.3: Digest Fields
DPoP permanent RFC 9449: OAuth 2.0 Demonstrating Proof of Possession (DPoP)
DPoP-Nonce permanent RFC 9449: OAuth 2.0 Demonstrating Proof of Possession (DPoP)
Early-Data permanent RFC 8470: Using Early Data in HTTP
EDIINT-Features provisional RFC 6017: Electronic Data Interchange - Internet Integration (EDIINT) Features Header Field
ETag permanent RFC 9110, Section 8.8.3: HTTP Semantics
Expect permanent RFC 9110, Section 10.1.1: HTTP Semantics
Expect-CT deprecated RFC 9163: Expect-CT Extension for HTTP Obsoleted by IESG; HTTPBIS
Expires permanent RFC 9111, Section 5.3: HTTP Caching
Ext obsoleted RFC 2774: An HTTP Extension Framework Status change of HTTP experiments to Historic
Forwarded permanent RFC 7239: Forwarded HTTP Extension
From permanent RFC 9110, Section 10.1.2: HTTP Semantics
GetProfile obsoleted Implementation of OPS Over HTTP
Hobareg permanent RFC 7486, Section 6.1.1: HTTP Origin-Bound Authentication (HOBA)
Host permanent RFC 9110, Section 7.2: HTTP Semantics
HTTP2-Settings obsoleted RFC 7540, Section 3.2.1: Hypertext Transfer Protocol Version 2 (HTTP/2) Obsolete; see Section 11.1 of RFC 9113
If permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
If-Match permanent RFC 9110, Section 13.1.1: HTTP Semantics
If-Modified-Since permanent RFC 9110, Section 13.1.3: HTTP Semantics
If-None-Match permanent RFC 9110, Section 13.1.2: HTTP Semantics
If-Range permanent RFC 9110, Section 13.1.5: HTTP Semantics
If-Schedule-Tag-Match permanent RFC 6338: Scheduling Extensions to CalDAV
If-Unmodified-Since permanent RFC 9110, Section 13.1.4: HTTP Semantics
IM permanent RFC 3229: Delta encoding in HTTP
Include-Referred-Token-Binding-ID permanent RFC 8473: Token Binding over HTTP
Incremental permanent Item RFC 10036: Incremental Forwarding of HTTP Messages
Isolation provisional OData Version 4.01 Part 1: Protocol; OASIS; Chet Ensign
Keep-Alive permanent RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1
Label permanent RFC 3253: Versioning Extensions to WebDAV: (Web Distributed Authoring and Versioning)
Last-Event-ID permanent HTML
Last-Modified permanent RFC 9110, Section 8.8.2: HTTP Semantics
Link permanent RFC 8288: Web Linking
Link-Template permanent RFC 9652: The Link-Template HTTP Header Field
Location permanent RFC 9110, Section 10.2.2: HTTP Semantics
Lock-Token permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
Man obsoleted RFC 2774: An HTTP Extension Framework Status change of HTTP experiments to Historic
Max-Forwards permanent RFC 9110, Section 7.6.2: HTTP Semantics
Memento-Datetime permanent RFC 7089: HTTP Framework for Time-Based Access to Resource States -- Memento
Meter permanent RFC 2227: Simple Hit-Metering and Usage-Limiting for HTTP
Method-Check obsoleted Access Control for Cross-site Requests
Method-Check-Expires obsoleted Access Control for Cross-site Requests
MIME-Version permanent RFC 9112, Appendix B.1: HTTP/1.1
Negotiate permanent RFC 2295: Transparent Content Negotiation in HTTP
NEL permanent Network Error Logging
No-Vary-Search permanent Dictionary RFC-ietf-httpbis-no-vary-search-10: The No-Vary-Search HTTP Caching Extension
OData-EntityId permanent OData Version 4.01 Part 1: Protocol; OASIS; Chet Ensign
OData-Isolation permanent OData Version 4.01 Part 1: Protocol; OASIS; Chet Ensign
OData-MaxVersion permanent OData Version 4.01 Part 1: Protocol; OASIS; Chet Ensign
OData-Version permanent OData Version 4.01 Part 1: Protocol; OASIS; Chet Ensign
Opt obsoleted RFC 2774: An HTTP Extension Framework Status change of HTTP experiments to Historic
Optional-WWW-Authenticate permanent RFC 8053, Section 3: HTTP Authentication Extensions for Interactive Clients
Ordering-Type permanent RFC 3648: Web Distributed Authoring and Versioning (WebDAV) Ordered Collections Protocol
Origin permanent RFC 6454: The Web Origin Concept
Origin-Agent-Cluster permanent Item HTML
OSCORE permanent RFC 8613, Section 11.1: Object Security for Constrained RESTful Environments (OSCORE)
OSLC-Core-Version permanent OASIS Project Specification 01; OASIS; Chet Ensign
Overwrite permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
P3P obsoleted The Platform for Privacy Preferences 1.0 (P3P1.0) Specification
PEP obsoleted PEP - an Extension Mechanism for HTTP
PEP-Info obsoleted PEP - an Extension Mechanism for HTTP
Permissions-Policy provisional Permissions Policy
PICS-Label obsoleted PICS Label Distribution Label Syntax and Communication Protocols
Ping-From permanent HTML
Ping-To permanent HTML
Position permanent RFC 3648: Web Distributed Authoring and Versioning (WebDAV) Ordered Collections Protocol
Pragma deprecated RFC 9111, Section 5.4: HTTP Caching
Prefer permanent RFC 7240: Prefer Header for HTTP
Preference-Applied permanent RFC 7240: Prefer Header for HTTP
Priority permanent Dictionary RFC 9218: Extensible Prioritization Scheme for HTTP
ProfileObject obsoleted Implementation of OPS Over HTTP
Protocol obsoleted PICS Label Distribution Label Syntax and Communication Protocols
Protocol-Info deprecated White Paper: Joint Electronic Payment Initiative
Protocol-Query deprecated White Paper: Joint Electronic Payment Initiative
Protocol-Request obsoleted PICS Label Distribution Label Syntax and Communication Protocols
Proxy-Authenticate permanent RFC 9110, Section 11.7.1: HTTP Semantics
Proxy-Authentication-Info permanent RFC 9110, Section 11.7.3: HTTP Semantics
Proxy-Authorization permanent RFC 9110, Section 11.7.2: HTTP Semantics
Proxy-Features obsoleted Notification for Proxy Caches
Proxy-Instruction obsoleted Notification for Proxy Caches
Proxy-Public-Address permanent List RFC-ietf-masque-connect-udp-listen-16: Proxying Bound UDP in HTTP
Proxy-Status permanent List RFC 9209: The Proxy-Status HTTP Response Header Field
Public obsoleted RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1
Public-Key-Pins permanent RFC 7469: Public Key Pinning Extension for HTTP
Public-Key-Pins-Report-Only permanent RFC 7469: Public Key Pinning Extension for HTTP
Range permanent RFC 9110, Section 14.2: HTTP Semantics
Redirect-Ref permanent RFC 4437: Web Distributed Authoring and Versioning (WebDAV) Redirect Reference Resources
Referer permanent RFC 9110, Section 10.1.3: HTTP Semantics
Referer-Root obsoleted Access Control for Cross-site Requests
Referrer-Policy permanent Referrer Policy The header name does not share the HTTP Referer header's misspelling.
Refresh permanent HTML
Repeatability-Client-ID provisional Repeatable Requests Version 1.0; OASIS; Chet Ensign
Repeatability-First-Sent provisional Repeatable Requests Version 1.0; OASIS; Chet Ensign
Repeatability-Request-ID provisional Repeatable Requests Version 1.0; OASIS; Chet Ensign
Repeatability-Result provisional Repeatable Requests Version 1.0; OASIS; Chet Ensign
Replay-Nonce permanent RFC 8555, Section 6.5.1: Automatic Certificate Management Environment (ACME)
Reporting-Endpoints provisional Reporting API
Repr-Digest permanent Dictionary RFC 9530, Section 3: Digest Fields
Retry-After permanent RFC 9110, Section 10.2.3: HTTP Semantics
Safe obsoleted RFC 2310: The Safe Response Header Field Status change of HTTP experiments to Historic
Schedule-Reply permanent RFC 6638: Scheduling Extensions to CalDAV
Schedule-Tag permanent RFC 6338: Scheduling Extensions to CalDAV
Sec-Fetch-Dest Permanent Item https://www.w3.org/TR/fetch-metadata/#sec-fetch-dest-header
Sec-Fetch-Mode Permanent Item https://www.w3.org/TR/fetch-metadata/#sec-fetch-mode-header
Sec-Fetch-Site Permanent Item https://www.w3.org/TR/fetch-metadata/#sec-fetch-site-header
Sec-Fetch-Storage-Access provisional Token https://privacycg.github.io/storage-access-headers
Sec-Fetch-User Permanent Item https://www.w3.org/TR/fetch-metadata/#sec-fetch-user-header
Sec-GPC provisional Global Privacy Control (GPC)
Sec-Purpose permanent Fetch Intended to replace the (not registered) Purpose and x-moz headers.
Sec-Token-Binding permanent RFC 8473: Token Binding over HTTP
Sec-WebSocket-Accept permanent RFC 6455: The WebSocket Protocol
Sec-WebSocket-Extensions permanent RFC 6455: The WebSocket Protocol
Sec-WebSocket-Key permanent RFC 6455: The WebSocket Protocol
Sec-WebSocket-Protocol permanent RFC 6455: The WebSocket Protocol
Sec-WebSocket-Version permanent RFC 6455: The WebSocket Protocol
Security-Scheme obsoleted RFC 2660: The Secure HyperText Transfer Protocol Status change of HTTP experiments to Historic
Server permanent RFC 9110, Section 10.2.4: HTTP Semantics
Server-Timing permanent Server Timing
Set-Cookie permanent RFC-ietf-httpbis-rfc6265bis-22, Section 5.8.1: Cookies: HTTP State Management Mechanism
Set-Cookie2 obsoleted RFC 2965: HTTP State Management Mechanism Obsoleted by RFC 6265: HTTP State Management Mechanism
Set-Txn permanent RFC 9967, Section 3: SCIM Profile for Security Event Tokens
SetProfile obsoleted Implementation of OPS Over HTTP
Signature permanent Dictionary RFC 9421, Section 4.2: HTTP Message Signatures
Signature-Input permanent Dictionary RFC 9421, Section 4.1: HTTP Message Signatures
SLUG permanent RFC 5023: The Atom Publishing Protocol
SoapAction permanent Simple Object Access Protocol (SOAP) 1.1
Status-URI permanent RFC 2518: HTTP Extensions for Distributed Authoring -- WEBDAV
Strict-Transport-Security permanent RFC 6797: HTTP Strict Transport Security (HSTS)
Sunset permanent RFC 8594: The Sunset HTTP Header Field
Surrogate-Capability provisional Edge Architecture Specification
Surrogate-Control provisional Edge Architecture Specification
TCN permanent RFC 2295: Transparent Content Negotiation in HTTP
TE permanent RFC 9110, Section 10.1.4: HTTP Semantics
Timeout permanent RFC 4918: HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
Timing-Allow-Origin provisional Resource Timing Level 1
Topic permanent RFC 8030, Section 5.4: Generic Event Delivery Using HTTP Push
Traceparent permanent Trace Context
Tracestate permanent Trace Context
Trailer permanent RFC 9110, Section 6.6.2: HTTP Semantics
Transfer-Encoding permanent RFC 9112, Section 6.1: HTTP Semantics
TTL permanent RFC 8030, Section 5.2: Generic Event Delivery Using HTTP Push
Unencoded-Digest permanent Dictionary RFC-ietf-httpbis-unencoded-digest-05, Section 3: HTTP Unencoded Digest
Upgrade permanent RFC 9110, Section 7.8: HTTP Semantics
Urgency permanent RFC 8030, Section 5.3: Generic Event Delivery Using HTTP Push
URI obsoleted RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1
Use-As-Dictionary permanent Dictionary RFC 9842, Section 2.1: Compression Dictionary Transport
User-Agent permanent RFC 9110, Section 10.1.5: HTTP Semantics
Variant-Vary permanent RFC 2295: Transparent Content Negotiation in HTTP
Vary permanent RFC 9110, Section 12.5.5: HTTP Semantics
Via permanent RFC 9110, Section 7.6.3: HTTP Semantics
Want-Content-Digest permanent Dictionary RFC 9530, Section 4: Digest Fields
Want-Digest obsoleted RFC 3230: Instance Digests in HTTP Obsoleted by RFC 9530, Section 1.3: Digest Fields
Want-Repr-Digest permanent Dictionary RFC 9530, Section 4: Digest Fields
Want-Unencoded-Digest permanent Dictionary RFC-ietf-httpbis-unencoded-digest-05, Section 4: HTTP Unencoded Digest
Warning obsoleted RFC 9111, Section 5.5: HTTP Caching
WWW-Authenticate permanent RFC 9110, Section 11.6.1: HTTP Semantics
X-Content-Type-Options permanent Fetch
X-Frame-Options permanent HTML
* permanent RFC 9110, Section 12.5.5: HTTP Semantics (reserved)

No-Vary-Search Dictionary Keys

Registration Procedure(s)

  • IETF Review

Reference

Available Formats

Key Description Reference
key-order Indicates if query parameter order affects caching RFC-ietf-httpbis-no-vary-search-10
params A list of query parameters that do not affect caching RFC-ietf-httpbis-no-vary-search-10
except A list of query parameters that affect caching RFC-ietf-httpbis-no-vary-search-10

Contact Information

Name Organization Contact URI Last Updated
Chet Ensign chet.ensign&oasis-open.org 2020-09-01
Chris Lemmons Chris_Lemmons&comcast.com 2024-08-06
Consumer Technology Association standards&cta.tech 2024-08-07
OASIS https://www.oasis-open.org