This API is in beta. It is only available to Chrome users on the beta channel and dev channel.

chrome.declarativeWebRequest

Description: Note: this API is currently on hold, without concrete plans to move to stable. Use the chrome.declarativeWebRequest API to intercept, block, or modify requests in-flight. It is significantly faster than the chrome.webRequest API because you can register rules that are evaluated in the browser rather than the JavaScript engine, which reduces roundtrip latencies and allows higher efficiency.
Availability: Beta and Dev channels only. Learn more.
Permissions: "declarativeWebRequest"
host permissions

Manifest

You must declare the "declarativeWebRequest" permission in the extension manifest to use this API, along with host permissions.

      {
        "name": "My extension",
        ...
        "permissions": [
          "declarativeWebRequest",
          "*://*/*"
        ],
        ...
      }
      

Note that certain types of non-sensitive actions do not require host permissions:

  • CancelRequest
  • IgnoreRules
  • RedirectToEmptyDocument
  • RedirectToTransparentImage

The SendMessageToExtension action requires host permissions for any hosts whose network requests you want to trigger a message.

All other actions require host permissions to all URLs.

As an example, if "*://*.google.com/*" is the only host permission an extension has, than such an extension may set up a rule to

  • cancel a request to "http://www.google.com" or "http://anything.else.com"
  • send a message when navigating to "http://www.google.com" but not to "http://something.else.com"
The extension cannot set up a rule to redirect "http://www.google.com" to "http://mail.google.com".

Rules

The Declarative Web Request API follows the concepts of the Declarative API. You can register rules to the chrome.declarativeWebRequest.onRequest event object.

The Declarative Web Request API supports a single type of match criteria, the RequestMatcher. The RequestMatcher matches network requests if and only if all listed criteria are met. The following RequestMatcher would match a network request when the user enters "http://www.example.com" in the URL bar:

      var matcher = new chrome.declarativeWebRequest.RequestMatcher({
        url: { hostSuffix: 'example.com', schemes: ['http'] },
        resourceType: ['main_frame']
        });
      

Requests to "https://www.example.com" would be rejected by the RequestMatcher due to the scheme. Also all requests for an embedded iframe would be rejected due to the resourceType.

Note: All conditions and actions are created via a constructor as shown in the example above.

In order to cancel all requests to "example.com", you can define a rule as follows:

      var rule = {
        conditions: [
          new chrome.declarativeWebRequest.RequestMatcher({
            url: { hostSuffix: 'example.com' } })
        ],
        actions: [
          new chrome.declarativeWebRequest.CancelRequest()
        ]};
      

In order to cancel all requests to "example.com" and "foobar.com", you can add a second condition, as each condition is sufficient to trigger all specified actions:

      var rule2 = {
        conditions: [
          new chrome.declarativeWebRequest.RequestMatcher({
            url: { hostSuffix: 'example.com' } }),
          new chrome.declarativeWebRequest.RequestMatcher({
            url: { hostSuffix: 'foobar.com' } })
        ],
        actions: [
          new chrome.declarativeWebRequest.CancelRequest()
        ]};
      

Register rules as follows:

      chrome.declarativeWebRequest.onRequest.addRules([rule2]);
      

Note: You should always register or unregister rules in bulk rather than individually because each of these operations recreates internal data structures. This re-creation is computationally expensive but facilitates a very fast URL matching algorithm for hundreds of thousands of URLs. The Performance section of the Events API provides further performance tips.

Evaluation of conditions and actions

The Declarative Web Request API follows the Life cycle model for web requests of the Web Request API. This means that conditions can only be tested at specific stages of a web request and, likewise, actions can also only be executed at specific stages. The following tables list the request stages that are compatible with conditions and actions.

Request stages during which condition attributes can be processed.
Condition attribute onBeforeRequest onBeforeSendHeaders onHeadersReceived onAuthRequired
url
resourceType
contentType
excludeContentType
responseHeaders
excludeResponseHeaders
requestHeaders
excludeRequestHeaders
thirdPartyForCookies
Request stages during which actions can be executed.
Event onBeforeRequest onBeforeSendHeaders onHeadersReceived onAuthRequired
AddRequestCookie
AddResponseCookie
AddResponseHeader
CancelRequest
EditRequestCookie
EditResponseCookie
IgnoreRules
RedirectByRegEx
RedirectRequest
RedirectToEmptyDocument
RedirectToTransparentImage
RemoveRequestCookie
RemoveRequestHeader
RemoveResponseCookie
RemoveResponseHeader
SendMessageToExtension
SetRequestHeader

Note: Applicable stages can be further constrained by using the "stages" attribute.

Note: Redirects initiated by a redirect action use the original request method for the redirect, with one exception: If the redirect is initiated at the onHeadersReceived stage, then the redirect will be issued using the GET method.

Example: It is possible to combine a new chrome.declarativeWebRequest.RequestMatcher({contentType: ["image/jpeg"]}) condition with a new chrome.declarativeWebRequest.CancelRequest() action because both of them can be evaluated in the onHeadersReceived stage. It is, however, impossible to combine the request matcher with a new chrome.declarativeWebRequest.SetRequestHeader() because request headers cannot be set any more by the time the content type has been terminated.

Using priorities to override rules

Rules can be associated with priorities as described in the Events API. This mechanism can be used to express exceptions. The following example will block all requests to images named "evil.jpg" except on the server "myserver.com".

      var rule1 = {
        priority: 100,
        conditions: [
          new chrome.declarativeWebRequest.RequestMatcher({
              url: { pathEquals: 'evil.jpg' } })
        ],
        actions: [
          new chrome.declarativeWebRequest.CancelRequest()
        ]
      };
      var rule2 = {
        priority: 1000,
        conditions: [
          new chrome.declarativeWebRequest.RequestMatcher({
            url: { hostSuffix: '.myserver.com' } })
        ],
        actions: [
          new chrome.declarativeWebRequest.IgnoreRules({
            lowerPriorityThan: 1000 })
        ]
      };
      chrome.declarativeWebRequest.onRequest.addRules([rule1, rule2]);
      

It is important to recognize that the IgnoreRules action is not persisted across request stages. All conditions of all rules are evaluated at each stage of a web request. If an IgnoreRules action is executed, it applies only to other actions that are executed for the same web request in the same stage.

Summary

Types
Stage
HeaderFilter
RequestMatcher
CancelRequest
RedirectRequest
RedirectToTransparentImage
RedirectToEmptyDocument
RedirectByRegEx
SetRequestHeader
RemoveRequestHeader
AddResponseHeader
RemoveResponseHeader
IgnoreRules
SendMessageToExtension
RequestCookie
ResponseCookie
FilterResponseCookie
AddRequestCookie
AddResponseCookie
EditRequestCookie
EditResponseCookie
RemoveRequestCookie
RemoveResponseCookie
Events
onRequest
onMessage

Types

Stage

Enum
"onBeforeRequest", "onBeforeSendHeaders", "onHeadersReceived", or "onAuthRequired"

HeaderFilter

Filters request headers for various criteria. Multiple criteria are evaluated as a conjunction.
properties
string (optional) namePrefix

Matches if the header name starts with the specified string.

string (optional) nameSuffix

Matches if the header name ends with the specified string.

array of string or string (optional) nameContains

Matches if the header name contains all of the specified strings.

string (optional) nameEquals

Matches if the header name is equal to the specified string.

string (optional) valuePrefix

Matches if the header value starts with the specified string.

string (optional) valueSuffix

Matches if the header value ends with the specified string.

array of string or string (optional) valueContains

Matches if the header value contains all of the specified strings.

string (optional) valueEquals

Matches if the header value is equal to the specified string.

RequestMatcher

Matches network events by various criteria.
properties
object (optional) url

Matches if the conditions of the UrlFilter are fulfilled for the URL of the request.

string (optional) hostContains

Matches if the host name of the URL contains a specified string. To test whether a host name component has a prefix 'foo', use hostContains: '.foo'. This matches 'www.foobar.com' and 'foo.com', because an implicit dot is added at the beginning of the host name. Similarly, hostContains can be used to match against component suffix ('foo.') and to exactly match against components ('.foo.'). Suffix- and exact-matching for the last components need to be done separately using hostSuffix, because no implicit dot is added at the end of the host name.

string (optional) hostEquals

Matches if the host name of the URL is equal to a specified string.

string (optional) hostPrefix

Matches if the host name of the URL starts with a specified string.

string (optional) hostSuffix

Matches if the host name of the URL ends with a specified string.

string (optional) pathContains

Matches if the path segment of the URL contains a specified string.

string (optional) pathEquals

Matches if the path segment of the URL is equal to a specified string.

string (optional) pathPrefix

Matches if the path segment of the URL starts with a specified string.

string (optional) pathSuffix

Matches if the path segment of the URL ends with a specified string.

string (optional) queryContains

Matches if the query segment of the URL contains a specified string.

string (optional) queryEquals

Matches if the query segment of the URL is equal to a specified string.

string (optional) queryPrefix

Matches if the query segment of the URL starts with a specified string.

string (optional) querySuffix

Matches if the query segment of the URL ends with a specified string.

string (optional) urlContains

Matches if the URL (without fragment identifier) contains a specified string. Port numbers are stripped from the URL if they match the default port number.

string (optional) urlEquals

Matches if the URL (without fragment identifier) is equal to a specified string. Port numbers are stripped from the URL if they match the default port number.

string (optional) urlMatches

Matches if the URL (without fragment identifier) matches a specified regular expression. Port numbers are stripped from the URL if they match the default port number. The regular expressions use the RE2 syntax.

string (optional) originAndPathMatches

Matches if the URL without query segment and fragment identifier matches a specified regular expression. Port numbers are stripped from the URL if they match the default port number. The regular expressions use the RE2 syntax.

string (optional) urlPrefix

Matches if the URL (without fragment identifier) starts with a specified string. Port numbers are stripped from the URL if they match the default port number.

string (optional) urlSuffix

Matches if the URL (without fragment identifier) ends with a specified string. Port numbers are stripped from the URL if they match the default port number.

array of string (optional) schemes

Matches if the scheme of the URL is equal to any of the schemes specified in the array.

array of integer or array of integer (optional) ports

Matches if the port of the URL is contained in any of the specified port lists. For example [80, 443, [1000, 1200]] matches all requests on port 80, 443 and in the range 1000-1200.

object (optional) firstPartyForCookiesUrl

Matches if the conditions of the UrlFilter are fulfilled for the 'first party' URL of the request. The 'first party' URL of a request, when present, can be different from the request's target URL, and describes what is considered 'first party' for the sake of third-party checks for cookies.

string (optional) hostContains

Matches if the host name of the URL contains a specified string. To test whether a host name component has a prefix 'foo', use hostContains: '.foo'. This matches 'www.foobar.com' and 'foo.com', because an implicit dot is added at the beginning of the host name. Similarly, hostContains can be used to match against component suffix ('foo.') and to exactly match against components ('.foo.'). Suffix- and exact-matching for the last components need to be done separately using hostSuffix, because no implicit dot is added at the end of the host name.

string (optional) hostEquals

Matches if the host name of the URL is equal to a specified string.

string (optional) hostPrefix

Matches if the host name of the URL starts with a specified string.

string (optional) hostSuffix

Matches if the host name of the URL ends with a specified string.

string (optional) pathContains

Matches if the path segment of the URL contains a specified string.

string (optional) pathEquals

Matches if the path segment of the URL is equal to a specified string.

string (optional) pathPrefix

Matches if the path segment of the URL starts with a specified string.

string (optional) pathSuffix

Matches if the path segment of the URL ends with a specified string.

string (optional) queryContains

Matches if the query segment of the URL contains a specified string.

string (optional) queryEquals

Matches if the query segment of the URL is equal to a specified string.

string (optional) queryPrefix

Matches if the query segment of the URL starts with a specified string.

string (optional) querySuffix

Matches if the query segment of the URL ends with a specified string.

string (optional) urlContains

Matches if the URL (without fragment identifier) contains a specified string. Port numbers are stripped from the URL if they match the default port number.

string (optional) urlEquals

Matches if the URL (without fragment identifier) is equal to a specified string. Port numbers are stripped from the URL if they match the default port number.

string (optional) urlMatches

Matches if the URL (without fragment identifier) matches a specified regular expression. Port numbers are stripped from the URL if they match the default port number. The regular expressions use the RE2 syntax.

string (optional) originAndPathMatches

Matches if the URL without query segment and fragment identifier matches a specified regular expression. Port numbers are stripped from the URL if they match the default port number. The regular expressions use the RE2 syntax.

string (optional) urlPrefix

Matches if the URL (without fragment identifier) starts with a specified string. Port numbers are stripped from the URL if they match the default port number.

string (optional) urlSuffix

Matches if the URL (without fragment identifier) ends with a specified string. Port numbers are stripped from the URL if they match the default port number.

array of string (optional) schemes

Matches if the scheme of the URL is equal to any of the schemes specified in the array.

array of integer or array of integer (optional) ports

Matches if the port of the URL is contained in any of the specified port lists. For example [80, 443, [1000, 1200]] matches all requests on port 80, 443 and in the range 1000-1200.

array of webRequest.ResourceType (optional) resourceType

Matches if the request type of a request is contained in the list. Requests that cannot match any of the types will be filtered out.

array of string (optional) contentType

Matches if the MIME media type of a response (from the HTTP Content-Type header) is contained in the list.

array of string (optional) excludeContentType

Matches if the MIME media type of a response (from the HTTP Content-Type header) is not contained in the list.

array of HeaderFilter (optional) requestHeaders

Matches if some of the request headers is matched by one of the HeaderFilters.

array of HeaderFilter (optional) excludeRequestHeaders

Matches if none of the request headers is matched by any of the HeaderFilters.

array of HeaderFilter (optional) responseHeaders

Matches if some of the response headers is matched by one of the HeaderFilters.

array of HeaderFilter (optional) excludeResponseHeaders

Matches if none of the response headers is matched by any of the HeaderFilters.

boolean (optional) thirdPartyForCookies

If set to true, matches requests that are subject to third-party cookie policies. If set to false, matches all other requests.

array of Stage (optional) stages

Contains a list of strings describing stages. Allowed values are 'onBeforeRequest', 'onBeforeSendHeaders', 'onHeadersReceived', 'onAuthRequired'. If this attribute is present, then it limits the applicable stages to those listed. Note that the whole condition is only applicable in stages compatible with all attributes.

CancelRequest

Declarative event action that cancels a network request.

RedirectRequest

Declarative event action that redirects a network request.
properties
string redirectUrl

Destination to where the request is redirected.

RedirectToTransparentImage

Declarative event action that redirects a network request to a transparent image.

RedirectToEmptyDocument

Declarative event action that redirects a network request to an empty document.

RedirectByRegEx

Redirects a request by applying a regular expression on the URL. The regular expressions use the RE2 syntax.
properties
string from

A match pattern that may contain capture groups. Capture groups are referenced in the Perl syntax ($1, $2, ...) instead of the RE2 syntax (\1, \2, ...) in order to be closer to JavaScript Regular Expressions.

string to

Destination pattern.

SetRequestHeader

Sets the request header of the specified name to the specified value. If a header with the specified name did not exist before, a new one is created. Header name comparison is always case-insensitive. Each request header name occurs only once in each request.
properties
string name

HTTP request header name.

string value

HTTP request header value.

RemoveRequestHeader

Removes the request header of the specified name. Do not use SetRequestHeader and RemoveRequestHeader with the same header name on the same request. Each request header name occurs only once in each request.
properties
string name

HTTP request header name (case-insensitive).

AddResponseHeader

Adds the response header to the response of this web request. As multiple response headers may share the same name, you need to first remove and then add a new response header in order to replace one.
properties
string name

HTTP response header name.

string value

HTTP response header value.

RemoveResponseHeader

Removes all response headers of the specified names and values.
properties
string name

HTTP request header name (case-insensitive).

string (optional) value

HTTP request header value (case-insensitive).

IgnoreRules

Masks all rules that match the specified criteria.
properties
integer (optional) lowerPriorityThan

If set, rules with a lower priority than the specified value are ignored. This boundary is not persisted, it affects only rules and their actions of the same network request stage.

string (optional) hasTag

If set, rules with the specified tag are ignored. This ignoring is not persisted, it affects only rules and their actions of the same network request stage. Note that rules are executed in descending order of their priorities. This action affects rules of lower priority than the current rule. Rules with the same priority may or may not be ignored.

SendMessageToExtension

Triggers the declarativeWebRequest.onMessage event.
properties
string message

The value that will be passed in the message attribute of the dictionary that is passed to the event handler.

RequestCookie

A filter or specification of a cookie in HTTP Requests.
properties
string (optional) name

Name of a cookie.

string (optional) value

Value of a cookie, may be padded in double-quotes.

ResponseCookie

A specification of a cookie in HTTP Responses.
properties
string (optional) name

Name of a cookie.

string (optional) value

Value of a cookie, may be padded in double-quotes.

string (optional) expires

Value of the Expires cookie attribute.

double (optional) maxAge

Value of the Max-Age cookie attribute

string (optional) domain

Value of the Domain cookie attribute.

string (optional) path

Value of the Path cookie attribute.

string (optional) secure

Existence of the Secure cookie attribute.

string (optional) httpOnly

Existence of the HttpOnly cookie attribute.

FilterResponseCookie

A filter of a cookie in HTTP Responses.
properties
string (optional) name

Name of a cookie.

string (optional) value

Value of a cookie, may be padded in double-quotes.

string (optional) expires

Value of the Expires cookie attribute.

double (optional) maxAge

Value of the Max-Age cookie attribute

string (optional) domain

Value of the Domain cookie attribute.

string (optional) path

Value of the Path cookie attribute.

string (optional) secure

Existence of the Secure cookie attribute.

string (optional) httpOnly

Existence of the HttpOnly cookie attribute.

integer (optional) ageUpperBound

Inclusive upper bound on the cookie lifetime (specified in seconds after current time). Only cookies whose expiration date-time is in the interval [now, now + ageUpperBound] fulfill this criterion. Session cookies and cookies whose expiration date-time is in the past do not meet the criterion of this filter. The cookie lifetime is calculated from either 'max-age' or 'expires' cookie attributes. If both are specified, 'max-age' is used to calculate the cookie lifetime.

integer (optional) ageLowerBound

Inclusive lower bound on the cookie lifetime (specified in seconds after current time). Only cookies whose expiration date-time is set to 'now + ageLowerBound' or later fulfill this criterion. Session cookies do not meet the criterion of this filter. The cookie lifetime is calculated from either 'max-age' or 'expires' cookie attributes. If both are specified, 'max-age' is used to calculate the cookie lifetime.

boolean (optional) sessionCookie

Filters session cookies. Session cookies have no lifetime specified in any of 'max-age' or 'expires' attributes.

AddRequestCookie

Adds a cookie to the request or overrides a cookie, in case another cookie of the same name exists already. Note that it is preferred to use the Cookies API because this is computationally less expensive.
properties

AddResponseCookie

Adds a cookie to the response or overrides a cookie, in case another cookie of the same name exists already. Note that it is preferred to use the Cookies API because this is computationally less expensive.
properties

EditRequestCookie

Edits one or more cookies of request. Note that it is preferred to use the Cookies API because this is computationally less expensive.
properties
declarativeWebRequest.RequestCookie filter

Filter for cookies that will be modified. All empty entries are ignored.

declarativeWebRequest.RequestCookie modification

Attributes that shall be overridden in cookies that machted the filter. Attributes that are set to an empty string are removed.

EditResponseCookie

Edits one or more cookies of response. Note that it is preferred to use the Cookies API because this is computationally less expensive.
properties
declarativeWebRequest.FilterResponseCookie filter

Filter for cookies that will be modified. All empty entries are ignored.

declarativeWebRequest.ResponseCookie modification

Attributes that shall be overridden in cookies that machted the filter. Attributes that are set to an empty string are removed.

RemoveRequestCookie

Removes one or more cookies of request. Note that it is preferred to use the Cookies API because this is computationally less expensive.
properties
declarativeWebRequest.RequestCookie filter

Filter for cookies that will be removed. All empty entries are ignored.

RemoveResponseCookie

Removes one or more cookies of response. Note that it is preferred to use the Cookies API because this is computationally less expensive.
properties
declarativeWebRequest.FilterResponseCookie filter

Filter for cookies that will be removed. All empty entries are ignored.

Events

onRequest

onMessage

Fired when a message is sent via declarativeWebRequest.SendMessageToExtension from an action of the declarative web request API.

addListener

chrome.declarativeWebRequest.onMessage.addListener(function callback)
Parameters
function callback

The callback parameter should be a function that looks like this:

function(object details) {...};
object details
string message

The message sent by the calling script.

Stage stage

The stage of the network request during which the event was triggered.

string requestId

The ID of the request. Request IDs are unique within a browser session. As a result, they could be used to relate different events of the same request.

string url
string method

Standard HTTP method.

integer frameId

The value 0 indicates that the request happens in the main frame; a positive value indicates the ID of a subframe in which the request happens. If the document of a (sub-)frame is loaded (type is main_frame or sub_frame), frameId indicates the ID of this frame, not the ID of the outer frame. Frame IDs are unique within a tab.

integer parentFrameId

ID of frame that wraps the frame which sent the request. Set to -1 if no parent frame exists.

integer tabId

The ID of the tab in which the request takes place. Set to -1 if the request isn't related to a tab.

webRequest.ResourceType type

How the requested resource will be used.

double timeStamp

The time when this signal is triggered, in milliseconds since the epoch.