HTTP headers let the client and the server pass additional information with a message in a request or response. In HTTP/1.X, a header is a case-insensitive name followed by a colon, then optional whitespace which will be ignored, and finally by its value (for example: Allow: POST ). In HTTP/2 and above, headers are displayed in lowercase when viewed in developer tools ( accept: */* ), and prefixed with a colon for a special group of pseudo-headers ( :status: 200 ). You can find more information on the syntax in each protocol version in the HTTP messages page.

Custom proprietary headers have historically been used with an X- prefix, but this convention was deprecated in 2012 because of the inconveniences it caused when nonstandard fields became standard in RFC 6648 ; others are listed in the IANA HTTP Field Name Registry , whose original content was defined in RFC 4229 . The IANA registry lists headers, including information about their status .

Headers can be grouped according to their contexts:

Request headers

Contain more information about the resource to be fetched, or about the client requesting the resource.

Response headers

Hold additional information about the response, like its location or about the server providing it.

Representation headers

Contain information about the body of the resource, like its MIME type , or encoding/compression applied.

Payload headers

Contain representation-independent information about payload data, including content length and the encoding used for transport.

Headers can also be grouped according to how proxies handle them:

End-to-end headers

These headers must be transmitted to the final recipient of the message: the server for a request, or the client for a response. Intermediate proxies must retransmit these headers unmodified and caches must store them.

Hop-by-hop headers

These headers are meaningful only for a single transport-level connection, and must not be retransmitted by proxies or cached. Note that only hop-by-hop headers may be set using the Connection header.

In this article

Authentication

Caching

Conditionals

Connection management

Content negotiation

Controls

Cookies

CORS

Downloads

Integrity digests

Integrity policy

Message body information

Preferences

Proxies

Range requests

Redirects

Request context

Response context

Security

Server-sent events

Transfer coding

WebSockets

Other

Experimental headers

Non-standard headers

Deprecated headers

See also

WWW-Authenticate

Defines the authentication method that should be used to access a resource.

Authorization

Contains the credentials to authenticate a user-agent with a server.

Proxy-Authenticate

Defines the authentication method that should be used to access a resource behind a proxy server.

Proxy-Authorization

Contains the credentials to authenticate a user agent with a proxy server.

Caching

The time, in seconds, that the object has been in a proxy cache.

Cache-Control

Directives for caching mechanisms in both requests and responses.

Clear-Site-Data

Clears browsing data (e.g., cookies, storage, cache) associated with the requesting website.

Expires

The date/time after which the response is considered stale.

No-Vary-Search Experimental

Specifies a set of rules that define how a URL's query parameters will affect cache matching. These rules dictate whether the same URL with different URL parameters should be saved as separate browser cache entries.

Conditionals

Last-Modified

The last modification date of the resource, used to compare several versions of the same resource. It is less accurate than ETag , but easier to calculate in some environments. Conditional requests using If-Modified-Since and If-Unmodified-Since use this value to change the behavior of the request.

A unique string identifying the version of the resource. Conditional requests using If-Match and If-None-Match use this value to change the behavior of the request.

If-Match

Makes the request conditional, and applies the method only if the stored resource matches one of the given ETags.

If-None-Match

Makes the request conditional, and applies the method only if the stored resource doesn't match any of the given ETags. This is used to update caches (for safe requests), or to prevent uploading a new resource when one already exists.

If-Modified-Since

Makes the request conditional, and expects the resource to be transmitted only if it has been modified after the given date. This is used to transmit data only when the cache is out of date.

If-Unmodified-Since

Makes the request conditional, and expects the resource to be transmitted only if it has not been modified after the given date. This ensures the coherence of a new fragment of a specific range with previous ones, or to implement an optimistic concurrency control system when modifying existing documents.

Determines how to match request headers to decide whether a cached response can be used rather than requesting a fresh one from the origin server.

Connection management

Connection

Controls whether the network connection stays open after the current transaction finishes.

Keep-Alive

Controls how long a persistent connection should stay open.

Content negotiation

For more details, refer to the Content negotiation article .

Accept

Informs the server about the types of data that can be sent back.

Accept-Encoding

The encoding algorithm, usually a compression algorithm , that can be used on the resource sent back.

Accept-Language

Informs the server about the human language the server is expected to send back. This is a hint and is not necessarily under the full control of the user: the server should always pay attention not to override an explicit user choice (like selecting a language from a dropdown).

Accept-Patch

A request content negotiation response header that advertises which media type the server is able to understand in a PATCH request.

Accept-Post

A request content negotiation response header that advertises which media type the server is able to understand in a POST request.

Controls

Expect

Indicates expectations that need to be fulfilled by the server to properly handle the request.

Max-Forwards

When using TRACE , indicates the maximum number of hops the request can do before being reflected to the sender.

Cookies

Cookie

Contains stored HTTP cookies previously sent by the server with the Set-Cookie header.

Set-Cookie

Send cookies from the server to the user-agent.

For more information, refer to the CORS documentation .

Access-Control-Allow-Credentials

Indicates whether the response to the request can be exposed when the credentials flag is true.

Access-Control-Allow-Headers

Used in response to a preflight request to indicate which HTTP headers can be used when making the actual request.

Access-Control-Allow-Methods

Specifies the methods allowed when accessing the resource in response to a preflight request.

Access-Control-Allow-Origin

Indicates whether the response can be shared.

Access-Control-Expose-Headers

Indicates which headers can be exposed as part of the response by listing their names.

Access-Control-Max-Age

Indicates how long the results of a preflight request can be cached.

Access-Control-Request-Headers

Used when issuing a preflight request to let the server know which HTTP headers will be used when the actual request is made.

Access-Control-Request-Method

Used when issuing a preflight request to let the server know which HTTP method will be used when the actual request is made.

Origin

Indicates where a fetch originates from.

Timing-Allow-Origin

Specifies origins that are allowed to see values of attributes retrieved via features of the Resource Timing API , which would otherwise be reported as zero due to cross-origin restrictions.

Downloads

Content-Disposition

Indicates if the resource transmitted should be displayed inline (default behavior without the header), or if it should be handled like a download and the browser should present a "Save As" dialog.

Integrity digests

Content-Digest Experimental

Provides a digest of the stream of octets framed in an HTTP message (the message content) dependent on Content-Encoding and Content-Range .

Repr-Digest Experimental

Provides a digest of the selected representation of the target resource before transmission. Unlike the Content-Digest , the digest does not consider Content-Encoding or Content-Range .

Want-Content-Digest Experimental

States the wish for a Content-Digest header. It is the Content- analogue of Want-Repr-Digest .

Want-Repr-Digest Experimental

States the wish for a Repr-Digest header. It is the Repr- analogue of Want-Content-Digest .

Integrity policy

Integrity-Policy

Ensures that all resources the user agent loads (of a certain type) have Subresource Integrity guarantees.

Integrity-Policy-Report-Only

Reports on resources that the user agent loads that would violate Subresource Integrity guarantees if the integrity policy were enforced (using the Integrity-Policy header).

Message body information

Content-Length

The size of the resource, in decimal number of bytes.

Content-Type

Indicates the media type of the resource.

Content-Encoding

Used to specify the compression algorithm.

Content-Language

Describes the human language(s) intended for the audience, so that it allows a user to differentiate according to the users' own preferred language.

Content-Location

Indicates an alternate location for the returned data.

Preferences

Preferences can be sent by clients in requests to indicate optional behaviors for requests and responses. The server response may indicate if a preference is applied, in cases where it would otherwise be ambiguous for the client. Browsers have no native handling for sending preferences via these headers; they are used in custom, implementation-specific clients.

Prefer

Indicates preferences for specific server behaviors during request processing. For example, it can request minimal response content ( return=minimal ) or asynchronous processing ( respond-async ). The server processes the request normally if the header is unsupported.

Preference-Applied

Informs the client which preferences specified in the Prefer header were applied by the server. It is a response-only header providing transparency about preference handling.

Proxies

Forwarded

Contains information from the client-facing side of proxy servers that is altered or lost when a proxy is involved in the path of the request.

Added by proxies, both forward and reverse proxies, and can appear in the request headers and the response headers.

Range requests

HTTP range requests allow the client to request a portion of a resource from the server. Range requests are useful for applications like media players that support random access, data tools that know they need only part of a large file, and download managers that let the user pause and resume a download.

Accept-Ranges

Indicates if the server supports range requests, and if so in which unit the range can be expressed.

Range

Indicates the part of a document that the server should return.

If-Range

Creates a conditional range request that is only fulfilled if the given etag or date matches the remote resource. Used to prevent downloading two ranges from incompatible version of the resource.

Content-Range

Indicates where in a full body message a partial message belongs.

Redirects

Location

Indicates the URL to redirect a page to.

Refresh

Directs the browser to reload the page or redirect to another. Takes the same value as the meta element with http-equiv="refresh" .

Request context

Contains an Internet email address for a human user who controls the requesting user agent.

Specifies the domain name of the server (for virtual hosting), and (optionally) the TCP port number on which the server is listening.

Referer

The address of the previous web page from which a link to the currently requested page was followed.

Referrer-Policy

Governs which referrer information sent in the Referer header should be included with requests made.

User-Agent

Contains a characteristic string that allows the network protocol peers to identify the application type, operating system, software vendor or software version of the requesting software user agent.

Response context

Allow

Lists the set of HTTP request methods supported by a resource.

Server

Contains information about the software used by the origin server to handle the request.

Security

Cross-Origin-Embedder-Policy (COEP)

Allows a server to declare an embedder policy for a given document.

Cross-Origin-Opener-Policy (COOP)

Prevents other domains from opening/controlling a window.

Cross-Origin-Resource-Policy (CORP)

Prevents other domains from reading the response of the resources to which this header is applied. See also CORP explainer article .

Content-Security-Policy ( CSP )

Controls resources the user agent is allowed to load for a given page.

Content-Security-Policy-Report-Only

Allows web developers to experiment with policies by monitoring, but not enforcing, their effects. These violation reports consist of JSON documents sent via an HTTP POST request to the specified URI.

Expect-CT Deprecated

Lets sites opt in to reporting and enforcement of Certificate Transparency to detect use of misissued certificates for that site.

Permissions-Policy

Provides a mechanism to allow and deny the use of browser features in a website's own frame, and in <iframe> s that it embeds.

Reporting-Endpoints Experimental

Response header that allows website owners to specify one or more endpoints used to receive errors such as CSP violation reports, Cross-Origin-Opener-Policy reports, or other generic violations.

Strict-Transport-Security ( HSTS )

Force communication using HTTPS instead of HTTP.

Upgrade-Insecure-Requests

Sends a signal to the server expressing the client's preference for an encrypted and authenticated response, and that it can successfully handle the upgrade-insecure-requests directive.

X-Content-Type-Options

Disables MIME sniffing and forces browser to use the type given in Content-Type .

X-Frame-Options (XFO)

Indicates whether a browser should be allowed to render a page in a <frame> , <iframe> , <embed> or <object> .

X-Permitted-Cross-Domain-Policies

A cross-domain policy file may grant clients, such as Adobe Acrobat or Apache Flex (among others), permission to handle data across domains that would otherwise be restricted due to the Same-Origin Policy . The X-Permitted-Cross-Domain-Policies header overrides such policy files so that clients still block unwanted requests.

X-Powered-By

May be set by hosting environments or other frameworks and contains information about them while not providing any usefulness to the application or its visitors. Unset this header to avoid exposing potential vulnerabilities.

X-XSS-Protection

Enables cross-site scripting filtering.

Fetch metadata request headers

Fetch metadata request headers provide information about the context from which the request originated. A server can use them to make decisions about whether a request should be allowed, based on where the request came from and how the resource will be used.

Sec-Fetch-Site

Indicates the relationship between a request initiator's origin and its target's origin. It is a Structured Header whose value is a token with possible values cross-site , same-origin , same-site , and none .

Sec-Fetch-Mode

Indicates the request's mode to a server. It is a Structured Header whose value is a token with possible values cors , navigate , no-cors , same-origin , and websocket .

Sec-Fetch-User

Indicates whether or not a navigation request was triggered by user activation. It is a Structured Header whose value is a boolean so possible values are ?0 for false and ?1 for true.

Sec-Fetch-Dest

Indicates the request's destination. It is a Structured Header whose value is a token with possible values audio , audioworklet , document , embed , empty , font , image , manifest , object , paintworklet , report , script , serviceworker , sharedworker , style , track , video , worker , and xslt .

The following request headers are not strictly "fetch metadata request headers", but similarly provide information about the context of how a resource will be used. A server might use them to modify its caching behavior, or the information that is returned:

Sec-Purpose

Indicates the purpose of the request, when the purpose is something other than immediate use by the user-agent. The header currently has one possible value, prefetch , which indicates that the resource is being fetched preemptively for a possible future navigation.

Service-Worker-Navigation-Preload

A request header sent in preemptive request to fetch() a resource during service worker boot. The value, which is set with NavigationPreloadManager.setHeaderValue() , can be used to inform a server that a different resource should be returned than in a normal fetch() operation.

Server-sent events

Reporting-Endpoints

Response header used to specify server endpoints where the browser should send warning and error reports when using the Reporting API .

Report-To Deprecated Non-standard

Response header used to specify server endpoints where the browser should send warning and error reports when using the Reporting API .

Transfer coding

Transfer-Encoding

Specifies the form of encoding used to safely transfer the resource to the user.

Specifies the transfer encodings the user agent is willing to accept.

Trailer

Allows the sender to include additional fields at the end of chunked message.

WebSockets

Headers used by the WebSockets API in the WebSocket handshake :

Sec-WebSocket-Accept

Response header that indicates that the server is willing to upgrade to a WebSocket connection.

Sec-WebSocket-Extensions

In requests, this header indicates the WebSocket extensions supported by the client in preferred order. In responses, it indicates the extension selected by the server from the client's preferences.

Sec-WebSocket-Key

Request header containing a key that verifies that the client explicitly intends to open a WebSocket .

Sec-WebSocket-Protocol

In requests, this header indicates the sub-protocols supported by the client in preferred order. In responses, it indicates the sub-protocol selected by the server from the client's preferences.

Sec-WebSocket-Version

In requests, this header indicates the version of the WebSocket protocol used by the client. In responses, it is sent only if the requested protocol version is not supported by the server, and lists the versions that the server supports.

Other

Alt-Svc

Used to list alternate ways to reach this service.

Alt-Used

Used to identify the alternative service in use.

Contains the date and time at which the message was originated.

This entity-header field provides a means for serializing one or more links in HTTP headers. It is semantically equivalent to the HTML <link> element.

Retry-After

Indicates how long the user agent should wait before making a follow-up request.

Server-Timing

Communicates one or more metrics and descriptions for the given request-response cycle.

Service-Worker

Included in fetches for a service worker's script resource. This header helps administrators log service worker script requests for monitoring purposes.

Service-Worker-Allowed

Used to remove the path restriction by including this header in the response of the Service Worker script .

SourceMap

Links to a source map so that debuggers can step through original source code instead of generated or transformed code.

Upgrade

This HTTP/1.1 (only) header can be used to upgrade an already established client/server connection to a different protocol (over the same transport protocol). For example, it can be used by a client to upgrade a connection from HTTP 1.1 to HTTP 2.0, or an HTTP or HTTPS connection into a WebSocket.

Priority

Provides a hint from about the priority of a particular resource request on a particular connection. The value can be sent in a request to indicate the client priority, or in a response if the server chooses to reprioritize the request.

Experimental headers

Attribution reporting headers

The Attribution Reporting API enables developers to measure conversions — for example when a user clicks an ad embedded on one site and then proceeds to purchase the item over on the vendor's site — and then access reports on those conversions. It does this without relying on third-party tracking cookies, instead relying on various headers to register sources and triggers that are matched to indicate a conversion.

Attribution-Reporting-Eligible

Used to indicate that the response corresponding to the current request is eligible to take part in attribution reporting, by registering either an attribution source or trigger.

Attribution-Reporting-Register-Source

Included as part of a response to a request that included an Attribution-Reporting-Eligible header, this is used to register an attribution source.

Attribution-Reporting-Register-Trigger

Included as part of a response to a request that included an Attribution-Reporting-Eligible header, this is used to register an attribution trigger.

Client hints

HTTP Client hints are a set of request headers that provide useful information about the client such as device type and network conditions, and allow servers to optimize what is served for those conditions.

Servers proactively requests the client hint headers they are interested in from the client using Accept-CH . The client may then choose to include the requested headers in subsequent requests.

Accept-CH

Servers can advertise support for Client Hints using the Accept-CH header field or an equivalent HTML <meta> element with http-equiv attribute.

Critical-CH Experimental

Servers use Critical-CH along with Accept-CH to specify that accepted client hints are also critical client hints .

The different categories of client hints are listed below.

User agent client hints

The UA client hints are request headers that provide information about the user agent, the platform/architecture it is running on, and user preferences set on the user agent or platform:

Sec-CH-UA Experimental

User agent's branding and version.

Sec-CH-UA-Arch Experimental

User agent's underlying platform architecture.

Sec-CH-UA-Bitness Experimental

User agent's underlying CPU architecture bitness (for example "64" bit).

Sec-CH-UA-Form-Factors Experimental

User agent's form-factors, describing how the user interacts with the user-agent.

Sec-CH-UA-Full-Version Deprecated

User agent's full version string.

Sec-CH-UA-Full-Version-List Experimental

Full version for each brand in the user agent's brand list.

Sec-CH-UA-Mobile Experimental

User agent is running on a mobile device or, more generally, prefers a "mobile" user experience.

Sec-CH-UA-Model Experimental

User agent's device model.

Sec-CH-UA-Platform Experimental

User agent's underlying operation system/platform.

Sec-CH-UA-Platform-Version Experimental

User agent's underlying operation system version.

Sec-CH-UA-WoW64 Experimental

Whether or not the user agent binary is running in 32-bit mode on 64-bit Windows.

Sec-CH-Prefers-Color-Scheme Experimental

User's preference of dark or light color scheme.

Sec-CH-Prefers-Reduced-Motion Experimental

User's preference to see fewer animations and content layout shifts.

Sec-CH-Prefers-Reduced-Transparency Experimental

Request header indicates the user agent's preference for reduced transparency.

Note: User-agent client hints are not available inside fenced frames because they rely on permissions policy delegation, which could be used to leak data.

Device client hints

Content-DPR Deprecated Non-standard

Response header used to confirm the image device to pixel ratio (DPR) in requests where the screen DPR client hint was used to select an image resource.

Device-Memory

Approximate amount of available client RAM memory. This is part of the Device Memory API .

Deprecated Non-standard

Request header that provides the client device pixel ratio (the number of physical device pixels for each CSS pixel ).

Viewport-Width Deprecated Non-standard

Request header provides the client's layout viewport width in CSS pixels .

Width Deprecated Non-standard

Request header indicates the desired resource width in physical pixels (the intrinsic size of an image).

Network client hints

Network client hints allow a server to choose what information is sent based on the user choice and network bandwidth and latency.

Downlink Experimental

Approximate bandwidth of the client's connection to the server, in Mbps. This is part of the Network Information API .

Experimental

The effective connection type ("network profile") that best matches the connection's latency and bandwidth. This is part of the Network Information API .

Experimental

Application layer round trip time (RTT) in milliseconds, which includes the server processing time. This is part of the Network Information API .

Save-Data Experimental

A string on that indicates the user agent's preference for reduced data usage.

Compression Dictionary Transport

Compression Dictionary Transport is a way of using a shared compression dictionary to reduce the transport size of HTTP responses rather than using the standard static dictionary in Brotli compression or Zstandard compression .

Available-Dictionary Experimental

A browser can use this request header to indicate the best dictionary it has available for the server to use for compression.

Dictionary-ID Experimental

Used when a browser already has a dictionary available for a resource and the server provided an id for the dictionary in the Use-As-Dictionary header. Requests for resources that can use the dictionary have an Available-Dictionary header and the server-provided dictionary id in the Dictionary-ID header.

Use-As-Dictionary Experimental

Lists the matching criteria that the dictionary can be used for in future requests.

Privacy

Deprecated Non-standard

Request header that indicates the user's tracking preference (Do Not Track). Deprecated in favor of Global Privacy Control (GPC), which is communicated to servers using the Sec-GPC header, and accessible to clients via navigator.globalPrivacyControl .

Deprecated Non-standard

Response header that indicates the tracking status that applied to the corresponding request. Used in conjunction with DNT.

Sec-GPC Non-standard Experimental

Indicates whether the user consents to a website or service selling or sharing their personal information with third parties.

Security

Origin-Agent-Cluster Experimental

Response header used to indicate that the associated Document should be placed in an origin-keyed agent cluster . This isolation allows user agents to allocate implementation-specific resources for agent clusters, such as processes or threads, more efficiently.

Server-sent events

Experimental

Defines a mechanism that enables developers to declare a network error reporting policy.

Topics API

The Topics API provides a mechanism for developers to implement use cases such as interest-based advertising (IBA). See the Topics API documentation for more information.

Observe-Browsing-Topics Experimental Non-standard

Response header used to mark topics of interest inferred from a calling site's URL as observed in the response to a request generated by a feature that enables the Topics API .

Sec-Browsing-Topics Experimental Non-standard

Request header that sends the selected topics for the current user along with the associated request, which are used by an ad tech platform to choose a personalized ad to display.

Other

Accept-Signature Experimental

A client can send the Accept-Signature header field to indicate intention to take advantage of any available signatures and to indicate what kinds of signatures it supports.

Early-Data Experimental

Indicates that the request has been conveyed in TLS early data.

Set-Login Experimental

Response header sent by a federated identity provider (IdP) to set its login status, meaning whether any users are logged into the IdP on the current browser or not. This is stored by the browser and used by the FedCM API .

Signature Experimental

The Signature header field conveys a list of signatures for an exchange, each one accompanied by information about how to determine the authority of and refresh that signature.

Signed-Headers Experimental

The Signed-Headers header field identifies an ordered list of response header fields to include in a signature.

Speculation-Rules Experimental

Provides a list of URLs pointing to text resources containing speculation rule JSON definitions. When the response is an HTML document, these rules will be added to the document's speculation rule set.

Sec-Speculation-Tags Experimental

Contains one or more tag values from the speculation rules that resulted in the speculation so a server can identify which rule(s) caused a speculation and potentially block them.

Supports-Loading-Mode Experimental

Set by a navigation target to opt-in to using various higher-risk loading modes. For example, cross-origin, same-site prerendering requires a Supports-Loading-Mode value of credentialed-prerender .

Non-standard headers

X-Forwarded-For Non-standard

Identifies the originating IP addresses of a client connecting to a web server through an HTTP proxy or a load balancer.

X-Forwarded-Host Non-standard

Identifies the original host requested that a client used to connect to your proxy or load balancer.

X-Forwarded-Proto Non-standard

Identifies the protocol (HTTP or HTTPS) that a client used to connect to your proxy or load balancer.

X-DNS-Prefetch-Control Non-standard

Controls DNS prefetching, a feature by which browsers proactively perform domain name resolution on both links that the user may choose to follow as well as URLs for items referenced by the document, including images, CSS, JavaScript, and so forth.

X-Robots-Tag Non-standard

The X-Robots-Tag HTTP header is used to indicate how a web page is to be indexed within public search engine results. The header is equivalent to <meta name="robots"> elements.

Deprecated headers

Pragma Deprecated

Implementation-specific header that may have various effects anywhere along the request-response chain. Used for backwards compatibility with HTTP/1.0 caches where the Cache-Control header is not yet present.

Warning Deprecated

General warning information about possible problems.

See also

Wikipedia page on List of HTTP headers

IANA registry

HTTP Working Group

Learn how to contribute

This page was last modified on ⁨Jul 4, 2025⁩ by MDN contributors . View this page on GitHub • Report a problem with this content

1. HTTP
2. Guides
3. Overview of HTTP
4. Evolution of HTTP
5. A typical HTTP session
6. HTTP messages
7. Media types
   1. Common types
8. Compression in HTTP
9. HTTP caching
10. HTTP authentication
11. Using HTTP cookies
12. Redirections in HTTP
13. Conditional requests
14. Range requests
15. Client hints
16. Compression Dictionary Transport Experimental
17. Network Error Logging Experimental
18. Content negotiation
    1. Default Accept values
19. Browser detection using the UA string
20. Connection management in HTTP/1.x
21. Protocol upgrade mechanism
22. Proxy servers and tunneling
    1. Proxy Auto-Configuration (PAC) file
23. Security and privacy

    1. HTTP Observatory
    2. Practical implementation guides
    3. Permissions Policy Experimental
    4. Cross-Origin Resource Policy (CORP)
    5. Cross-Origin Resource Sharing (CORS)
    6. CORS errors

       1. Reason: CORS disabled
       2. Reason: CORS header 'Access-Control-Allow-Origin' does not match 'xyz'
       3. Reason: CORS header 'Access-Control-Allow-Origin' missing
       4. Reason: CORS header 'Origin' cannot be added
       5. Reason: CORS preflight channel did not succeed
       6. Reason: CORS request did not succeed
       7. Reason: CORS request external redirect not allowed
       8. Reason: CORS request not HTTP
       9. Reason: Credential is not supported if the CORS header 'Access-Control-Allow-Origin' is '*'
       10. Reason: Did not find method in CORS header 'Access-Control-Allow-Methods'
       11. Reason: expected 'true' in CORS header 'Access-Control-Allow-Credentials'
       12. Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Headers'
       13. Reason: invalid token 'xyz' in CORS header 'Access-Control-Allow-Methods'
       14. Reason: missing token 'xyz' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel
       15. Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed
    7. Content Security Policy (CSP)

       1. Errors and warnings
24. Reference
25. HTTP headers

    1. Accept
    2. Accept-CH
    3. Accept-Encoding
    4. Accept-Language
    5. Accept-Patch
    6. Accept-Post
    7. Accept-Ranges
    8. Access-Control-Allow-Credentials
    9. Access-Control-Allow-Headers
    10. Access-Control-Allow-Methods
    11. Access-Control-Allow-Origin
    12. Access-Control-Expose-Headers
    13. Access-Control-Max-Age
    14. Access-Control-Request-Headers
    15. Access-Control-Request-Method
    16. Age
    17. Allow
    18. Alt-Svc
    19. Alt-Used
    20. Attribution-Reporting-Eligible Experimental
    21. Attribution-Reporting-Register-Source Experimental
    22. Attribution-Reporting-Register-Trigger Experimental
    23. Authorization
    24. Available-Dictionary Experimental
    25. Cache-Control
    26. Clear-Site-Data
    27. Connection
    28. Content-Digest
    29. Content-Disposition
    30. Content-DPR Non-standard Deprecated
    31. Content-Encoding
    32. Content-Language
    33. Content-Length
    34. Content-Location
    35. Content-Range
    36. Content-Security-Policy
    37. Content-Security-Policy-Report-Only
    38. Content-Type
    39. Cookie
    40. Critical-CH Experimental
    41. Cross-Origin-Embedder-Policy
    42. Cross-Origin-Opener-Policy
    43. Cross-Origin-Resource-Policy
    44. Date
    45. Device-Memory
    46. Dictionary-ID Experimental Non-standard Deprecated
    47. Downlink Experimental Non-standard Deprecated
    48. Early-Data Experimental Experimental
    49. ETag
    50. Expect
    51. Expect-CT Deprecated
    52. Expires
    53. Forwarded
    54. From
    55. Host
    56. If-Match
    57. If-Modified-Since
    58. If-None-Match
    59. If-Range
    60. If-Unmodified-Since
    61. Integrity-Policy Experimental
    62. Integrity-Policy-Report-Only Experimental
    63. Keep-Alive
    64. Last-Modified
    65. Link
    66. Location
    67. Max-Forwards
    68. NEL Experimental
    69. No-Vary-Search Experimental
    70. Observe-Browsing-Topics Experimental Non-standard
    71. Origin
    72. Origin-Agent-Cluster
    73. Permissions-Policy Experimental
    74. Pragma Deprecated
    75. Prefer
    76. Preference-Applied
    77. Priority
    78. Proxy-Authenticate
    79. Proxy-Authorization
    80. Range
    81. Referer
    82. Referrer-Policy
    83. Refresh
    84. Report-To Non-standard Deprecated
    85. Reporting-Endpoints
    86. Repr-Digest
    87. Retry-After
    88. RTT Experimental
    89. Save-Data Experimental
    90. Sec-Browsing-Topics Experimental Non-standard
    91. Sec-CH-Prefers-Color-Scheme Experimental
    92. Sec-CH-Prefers-Reduced-Motion Experimental
    93. Sec-CH-Prefers-Reduced-Transparency Experimental
    94. Sec-CH-UA Experimental
    95. Sec-CH-UA-Arch Experimental
    96. Sec-CH-UA-Bitness Experimental
    97. Sec-CH-UA-Form-Factors Experimental
    98. Sec-CH-UA-Full-Version Deprecated
    99. Sec-CH-UA-Full-Version-List Experimental
    100. Sec-CH-UA-Mobile Experimental
    101. Sec-CH-UA-Model Experimental
    102. Sec-CH-UA-Platform Experimental
    103. Sec-CH-UA-Platform-Version Experimental
    104. Sec-CH-UA-WoW64 Experimental
    105. Sec-Fetch-Dest
    106. Sec-Fetch-Mode
    107. Sec-Fetch-Site
    108. Sec-Fetch-User
    109. Sec-GPC Experimental
    110. Sec-Purpose
    111. Sec-Speculation-Tags Experimental
    112. Sec-WebSocket-Accept
    113. Sec-WebSocket-Extensions
    114. Sec-WebSocket-Key
    115. Sec-WebSocket-Protocol
    116. Sec-WebSocket-Version
    117. Server
    118. Server-Timing
    119. Service-Worker
    120. Service-Worker-Allowed
    121. Service-Worker-Navigation-Preload
    122. Set-Cookie
    123. Set-Login
    124. SourceMap
    125. Speculation-Rules Experimental
    126. Strict-Transport-Security
    127. Supports-Loading-Mode Experimental
    128. TE
    129. Timing-Allow-Origin
    130. Tk Non-standard Deprecated
    131. Trailer
    132. Transfer-Encoding
    133. Upgrade
    134. Upgrade-Insecure-Requests
    135. Use-As-Dictionary Experimental
    136. User-Agent
    137. Vary
    138. Via
    139. Viewport-Width Non-standard Deprecated
    140. Want-Content-Digest
    141. Want-Repr-Digest
    142. Warning Deprecated
    143. Width Non-standard Deprecated
    144. WWW-Authenticate
    145. X-Content-Type-Options
    146. X-DNS-Prefetch-Control Non-standard
    147. X-Forwarded-For Non-standard
    148. X-Forwarded-Host Non-standard
    149. X-Forwarded-Proto Non-standard
    150. X-Frame-Options
    151. X-Permitted-Cross-Domain-Policies Non-standard
    152. X-Powered-By Non-standard
    153. X-Robots-Tag Non-standard
    154. X-XSS-Protection Non-standard Deprecated
26. HTTP request methods

    1. CONNECT
    2. DELETE
    3. GET
    4. HEAD
    5. OPTIONS
    6. PATCH
    7. POST
    8. PUT
    9. TRACE
27. HTTP response status codes

    1. 100 Continue
    2. 101 Switching Protocols
    3. 102 Processing
    4. 103 Early Hints
    5. 200 OK
    6. 201 Created
    7. 202 Accepted
    8. 203 Non-Authoritative Information
    9. 204 No Content
    10. 205 Reset Content
    11. 206 Partial Content
    12. 207 Multi-Status
    13. 208 Already Reported
    14. 226 IM Used
    15. 300 Multiple Choices
    16. 301 Moved Permanently
    17. 302 Found
    18. 303 See Other
    19. 304 Not Modified
    20. 307 Temporary Redirect
    21. 308 Permanent Redirect
    22. 400 Bad Request
    23. 401 Unauthorized
    24. 402 Payment Required
    25. 403 Forbidden
    26. 404 Not Found
    27. 405 Method Not Allowed
    28. 406 Not Acceptable
    29. 407 Proxy Authentication Required
    30. 408 Request Timeout
    31. 409 Conflict
    32. 410 Gone
    33. 411 Length Required
    34. 412 Precondition Failed
    35. 413 Content Too Large
    36. 414 URI Too Long
    37. 415 Unsupported Media Type
    38. 416 Range Not Satisfiable
    39. 417 Expectation Failed
    40. 418 I'm a teapot
    41. 421 Misdirected Request
    42. 422 Unprocessable Content
    43. 423 Locked
    44. 424 Failed Dependency
    45. 425 Too Early
    46. 426 Upgrade Required
    47. 428 Precondition Required
    48. 429 Too Many Requests
    49. 431 Request Header Fields Too Large
    50. 451 Unavailable For Legal Reasons
    51. 500 Internal Server Error
    52. 501 Not Implemented
    53. 502 Bad Gateway
    54. 503 Service Unavailable
    55. 504 Gateway Timeout
    56. 505 HTTP Version Not Supported
    57. 506 Variant Also Negotiates
    58. 507 Insufficient Storage
    59. 508 Loop Detected
    60. 510 Not Extended
    61. 511 Network Authentication Required
28. CSP directives

    1. base-uri
    2. block-all-mixed-content Deprecated
    3. child-src
    4. connect-src
    5. default-src
    6. fenced-frame-src Experimental
    7. font-src
    8. form-action
    9. frame-ancestors
    10. frame-src
    11. img-src
    12. manifest-src
    13. media-src
    14. object-src
    15. prefetch-src Non-standard Deprecated
    16. report-to
    17. report-uri Deprecated
    18. require-trusted-types-for
    19. sandbox
    20. script-src
    21. script-src-attr
    22. script-src-elem
    23. style-src
    24. style-src-attr
    25. style-src-elem
    26. trusted-types
    27. upgrade-insecure-requests
    28. worker-src
29. Permissions-Policy directives Experimental

    1. accelerometer Experimental
    2. ambient-light-sensor Experimental
    3. aria-notify Experimental Non-standard
    4. attribution-reporting Experimental
    5. autoplay Experimental
    6. bluetooth Experimental
    7. browsing-topics Experimental Non-standard
    8. camera Experimental
    9. captured-surface-control Experimental
    10. compute-pressure Experimental
    11. cross-origin-isolated Experimental
    12. deferred-fetch Experimental
    13. deferred-fetch-minimal Experimental
    14. display-capture Experimental
    15. encrypted-media Experimental
    16. fullscreen Experimental
    17. gamepad Experimental
    18. geolocation Experimental
    19. gyroscope Experimental Experimental
    20. identity-credentials-get Experimental
    21. idle-detection Experimental
    22. language-detector Experimental
    23. local-fonts Experimental
    24. magnetometer Experimental
    25. microphone Experimental Experimental
    26. on-device-speech-recognition Experimental
    27. otp-credentials Experimental
    28. payment Experimental
    29. picture-in-picture Experimental
    30. publickey-credentials-create Experimental
    31. publickey-credentials-get Experimental
    32. screen-wake-lock Experimental
    33. serial Experimental
    34. speaker-selection Experimental
    35. storage-access Experimental
    36. summarizer Experimental
    37. translator Experimental Experimental
    38. web-share Experimental
    39. window-management Experimental
    40. xr-spatial-tracking Experimental
30. HTTP resources and specifications