A free utility to help web developers watch and manipulate network traffic from their AJAX applications.
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Latest commit 1b2d859 Feb 4, 2017 @jekh jekh committed on GitHub Merge pull request #604 from jekh/update-trust-store
Updated to 2017-01-18 version of Mozilla CA list


BrowserMob Proxy

BrowserMob Proxy allows you to manipulate HTTP requests and responses, capture HTTP content, and export performance data as a HAR file. BMP works well as a standalone proxy server, but it is especially useful when embedded in Selenium tests.

The latest version of BrowserMob Proxy is 2.1.4, powered by LittleProxy.

If you're running BrowserMob Proxy within a Java application or Selenium test, get started with Embedded Mode. If you want to run BMP from the command line as a standalone proxy, start with Standalone.

Getting started: Embedded Mode

To use BrowserMob Proxy in your tests or application, add the browsermob-core dependency to your pom:


Start the proxy:

    BrowserMobProxy proxy = new BrowserMobProxyServer();
    int port = proxy.getPort(); // get the JVM-assigned port
    // Selenium or HTTP client configuration goes here

Then configure your HTTP client to use a proxy running at the specified port.

Using with Selenium? See the Using with Selenium section.

Getting started: Standalone

To run in standalone mode from the command line, first download the latest release from the releases page, or build the latest from source.

Start the REST API:

    ./browsermob-proxy -port 8080

Then create a proxy server instance:

    curl -X POST http://localhost:8080/proxy

The "port" is the port of the newly-created proxy instance, so configure your HTTP client or web browser to use a proxy on the returned port. For more information on the features available in the REST API, see the REST API documentation.

Changes since 2.0.0

The new BrowserMobProxyServer class has replaced the legacy ProxyServer implementation. The legacy implementation is no longer actively supported; all new code should use BrowserMobProxyServer. We highly recommend that existing code migrate to the new implementation.

The most important changes from 2.0 are:

New BrowserMobProxy API

BrowserMob Proxy 2.1 includes a new BrowserMobProxy interface to interact with BrowserMob Proxy programmatically. The new interface defines the functionality that BrowserMob Proxy will support in future releases (including 3.0+). To ease migration, both the legacy (Jetty-based) ProxyServer class and the new, LittleProxy-powered BrowserMobProxy class support the new BrowserMobProxy interface.

We highly recommend migrating existing code to the BrowserMobProxy interface using the BrowserMobProxyServer class.

Using the LittleProxy implementation with 2.0.0 code

The legacy interface, implicitly defined by the ProxyServer class, has been extracted into net.lightbody.bmp.proxy.LegacyProxyServer and is now officially deprecated. The new LittleProxy-based implementation will implement LegacyProxyServer for all 2.1.x releases. This means you can switch to the LittleProxy-powered implementation with minimal change to existing code (with the exception of interceptors):

    // With the Jetty-based 2.0.0 release, BMP was created like this:
    ProxyServer proxyServer = new ProxyServer();
    // [...]

    // To use the LittleProxy-powered 2.1.4 release, simply change to
    // the LegacyProxyServer interface and the adapter for the new
    // LittleProxy-based implementation:
    LegacyProxyServer proxyServer = new BrowserMobProxyServerLegacyAdapter();
    // Almost all deprecated 2.0.0 methods are supported by the 
    // new BrowserMobProxyServerLegacyAdapter implementation, so in most cases,
    // no further code changes are necessary

LegacyProxyServer will not be supported after 3.0 is released, so we recommend migrating to the BrowserMobProxy interface as soon as possible. The new interface provides additional functionality and is compatible with both the legacy Jetty-based ProxyServer implementation (with some exceptions) and the new LittleProxy implementation.

If you must continue using the legacy Jetty-based implementation, include the browsermob-core-legacy artifact instead of browsermob-core.

Features and Usage

The proxy is programmatically controlled via a REST interface or by being embedded directly inside Java-based programs and unit tests. It captures performance data in the HAR format. In addition it can actually control HTTP traffic, such as:

  • blacklisting and whitelisting certain URL patterns
  • simulating various bandwidth and latency
  • remapping DNS lookups
  • flushing DNS caching
  • controlling DNS and request timeouts
  • automatic BASIC authorization


New in 2.1: LittleProxy is the default implementation of the REST API. You may specify --use-littleproxy false to disable LittleProxy in favor of the legacy Jetty 5-based implementation.

To get started, first start the proxy by running browsermob-proxy or browsermob-proxy.bat in the bin directory:

$ sh browsermob-proxy -port 8080
INFO 05/31 03:12:48 o.b.p.Main           - Starting up...
2011-05-30 20:12:49.517:INFO::jetty-7.3.0.v20110203
2011-05-30 20:12:49.689:INFO::started o.e.j.s.ServletContextHandler{/,null}
2011-05-30 20:12:49.820:INFO::Started SelectChannelConnector@

Once started, there won't be an actual proxy running until you create a new proxy. You can do this by POSTing to /proxy:

[~]$ curl -X POST http://localhost:8080/proxy

or optionally specify your own port:

[~]$ curl -X POST -d 'port=8089' http://localhost:8080/proxy

or if running BrowserMob Proxy in a multi-homed environment, specify a desired bind address (default is

[~]$ curl -X POST -d 'bindAddress=' http://localhost:8080/proxy

Once that is done, a new proxy will be available on the port returned. All you have to do is point a browser to that proxy on that port and you should be able to browse the internet. The following additional APIs will then be available:

Description HTTP method Request path Request parameters
Get a list of ports attached to ProxyServer instances managed by ProxyManager GET /proxy
Creates a new HAR attached to the proxy and returns the HAR content if there was a previous HAR. [port] in request path it is port where your proxy was started PUT /proxy/[port]/har

captureHeaders - Boolean, capture headers or not. Optional, default to "false".

captureContent - Boolean, capture content bodies or not. Optional, default to "false".

captureBinaryContent - Boolean, capture binary content or not. Optional, default to "false".

initialPageRef - The string name of The first page ref that should be used in the HAR. Optional, default to "Page 1".

initialPageTitle - The title of first HAR page. Optional, default to initialPageRef.

Starts a new page on the existing HAR. [port] in request path it is port where your proxy was started PUT /proxy/[port]/har/pageRef

pageRef - The string name of the first page ref that should be used in the HAR. Optional, default to "Page N" where N is the next page number.

pageTitle - The title of new HAR page. Optional, default to pageRef.

Shuts down the proxy and closes the port. [port] in request path it is port where your proxy was started DELETE /proxy/[port]
Returns the JSON/HAR content representing all the HTTP traffic passed through the proxy (provided you have already created the HAR with this method) GET /proxy/[port]/har
Displays whitelisted items GET /proxy/[port]/whitelist
Sets a list of URL patterns to whitelist PUT /proxy/[port]/whitelist

regex - A comma separated list of regular expressions.

status - The HTTP status code to return for URLs that do not match the whitelist.

Clears all URL patterns from the whitelist DELETE /proxy/[port]/whitelist
Displays blacklisted items GET /proxy/[port]/blacklist
Set a URL to blacklist PUT /proxy/[port]/blacklist

regex - The blacklist regular expression.

status - The HTTP status code to return for URLs that are blacklisted.

method - The regular expression for matching HTTP method (GET, POST, PUT, etc). Optional, by default processing all HTTP method.

Clears all URL patterns from the blacklist DELETE /proxy/[port]/blacklist
Limit the bandwidth through the proxy on the [port] PUT /proxy/[port]/limit

downstreamKbps - Sets the downstream bandwidth limit in kbps. Optional.

upstreamKbps - Sets the upstream bandwidth limit kbps. Optional, by default unlimited.

downstreamMaxKB - Specifies how many kilobytes in total the client is allowed to download through the proxy. Optional, by default unlimited.

upstreamMaxKB - Specifies how many kilobytes in total the client is allowed to upload through the proxy. Optional, by default unlimited.

latency - Add the given latency to each HTTP request. Optional, by default all requests are invoked without latency.

enable - A boolean that enable bandwidth limiter. Optional, by default to "false", but setting any of the properties above will implicitly enable throttling

payloadPercentage - Specifying what percentage of data sent is payload, e.g. use this to take into account overhead due to tcp/ip. Optional.

maxBitsPerSecond - The max bits per seconds you want this instance of StreamManager to respect. Optional.

Displays the amount of data remaining to be uploaded/downloaded until the limit is reached GET /proxy/[port]/limit
Set and override HTTP Request headers POST /proxy/[port]/headers Payload data should be JSON encoded set of headers. Where key is a header name (such as "User-Agent") and value is a value of HTTP header to setup (such as "BrowserMob-Agent"). Example: {"User-Agent": "BrowserMob-Agent"}
Overrides normal DNS lookups and remaps the given hosts with the associated IP address POST /proxy/[port]/hosts Payload data should be JSON encoded set of hosts. Where key is a host name (such as "example.com") and value is a IP address which associatied with host hame (such as ""'). Example: {"example.com": ""}
Sets automatic basic authentication for the specified domain POST /proxy/[port]/auth/basic/[domain] Payload data should be JSON encoded username and password name/value pairs. Example: {"username": "myUsername", "password": "myPassword"}
Wait till all request are being made PUT /proxy/[port]/wait

quietPeriodInMs - Wait till all request are being made. Optional.

timeoutInMs - Sets quiet period in milliseconds. Optional.

Handles different proxy timeouts PUT proxy/[port]/timeout

Payload data should be JSON encoded set of parameters. Where key is a parameters name (such as "connectionTimeout") and value is a value of parameter to setup (such as "500")

requestTimeout - Request timeout in milliseconds. A timeout value of -1 is interpreted as infinite timeout. Optional, default to "-1".

readTimeout - Read timeout in milliseconds. Which is the timeout for waiting for data or, put differently, a maximum period inactivity between two consecutive data packets). A timeout value of zero is interpreted as an infinite timeout. Optional, default to "60000".

connectionTimeout - Determines the timeout in milliseconds until a connection is established. A timeout value of zero is interpreted as an infinite timeout. Optional, default to "60000".

dnsCacheTimeout - Sets the maximum length of time that records will be stored in this Cache. A nonpositive value disables this feature (that is, sets no limit). Optional, default to "0".

Example: {"connectionTimeout" : "500", "readTimeout" : "200"}
Redirecting URL's PUT /proxy/[port]/rewrite

matchRegex - A matching URL regular expression.

replace - replacement URL.

Removes all URL redirection rules currently in effect DELETE /proxy/[port]/rewrite
Setting the retry count PUT /proxy/[port]/retry

retrycount - The number of times a method will be retried.

Empties the DNS cache DELETE /proxy/[port]/dns/cache
REST API interceptors with LittleProxy
Describe your own request interception POST /proxy/[port]/filter/request A string wich determinates interceptor rules. See more here
Describe your own response interception POST /proxy/[port]/filter/response A string wich determinates interceptor rules. See more here
REST API with Legacy interceptors
Describe your own request interception POST /proxy/[port]/interceptor/request A string wich determinates interceptor rules. See more here
Describe your own response interception POST /proxy/[port]/interceptor/response A string wich determinates interceptor rules. See more here

For example, once you've started the proxy you can create a new HAR to start recording data like so:

[~]$ curl -X PUT -d 'initialPageRef=Foo' http://localhost:8080/proxy/8081/har

Now when traffic goes through port 9091 it will be attached to a page reference named "Foo". Consult the HAR specification for more info on what a "pageRef" is. You can also start a new pageRef like so:

[~]$ curl -X PUT -d 'pageRef=Bar' http://localhost:8080/proxy/8081/har/pageRef

That will ensure no more HTTP requests get attached to the old pageRef (Foo) and start getting attached to the new pageRef (Bar). After creating the HAR, you can get its content at any time like so:

[~]$ curl http://localhost:8080/proxy/8081/har

Sometimes you will want to route requests through an upstream proxy server. In this case specify your proxy server by adding the httpProxy parameter to your create proxy request:

[~]$ curl -X POST http://localhost:8080/proxy?httpProxy=yourproxyserver.com:8080

Alternatively, you can specify the upstream proxy config for all proxies created using the standard JVM system properties for HTTP proxies. Note that you can still override the default upstream proxy via the POST payload, but if you omit the payload the JVM system properties will be used to specify the upstream proxy.

Command-line Arguments

  • -port <port>
    • Port on which the API listens. Default value is 8080.
  • -address
    • Address to which the API is bound. Default value is
  • -proxyPortRange <from>-<to>
    • Range of ports reserved for proxies. Only applies if port parameter is not supplied in the POST request. Default values are <port>+1 to <port>+500+1.
  • -ttl <seconds>
    • Proxy will be automatically deleted after a specified time period. Off by default.

Embedded Mode

New in 2.1: New Embedded Mode module

New in 2.1: New BrowserMobProxy interface for Embedded Mode

BrowserMob Proxy 2.1 separates the Embedded Mode and REST API into two modules. If you only need Embedded Mode functionality, add the browsermob-core artifact as a dependency. The REST API artifact is browsermob-rest.

If you're using Java and Selenium, the easiest way to get started is to embed the project directly in your test. First, you'll need to make sure that all the dependencies are imported in to the project. You can find them in the lib directory. Or, if you're using Maven, you can add this to your pom:


Once done, you can start a proxy using net.lightbody.bmp.BrowserMobProxy:

    BrowserMobProxy proxy = new BrowserMobProxyServer();
    // get the JVM-assigned port and get to work!
    int port = proxy.getPort();

Consult the Javadocs on the net.lightbody.bmp.BrowserMobProxy class for the full API.

Using With Selenium

Selenium 3 users: Due to a geckodriver issue, Firefox 51 and lower do not properly support proxies with WebDriver's DesiredCapabilities. See this answer for a suitable work-around.

BrowserMob Proxy makes it easy to use a proxy in Selenium tests:

    // start the proxy
    BrowserMobProxy proxy = new BrowserMobProxyServer();

    // get the Selenium proxy object
    Proxy seleniumProxy = ClientUtil.createSeleniumProxy(proxy);

    // configure it as a desired capability
    DesiredCapabilities capabilities = new DesiredCapabilities();
    capabilities.setCapability(CapabilityType.PROXY, seleniumProxy);

    // start the browser up
    WebDriver driver = new FirefoxDriver(capabilities);

    // enable more detailed HAR capture, if desired (see CaptureType for the complete list)
    proxy.enableHarCaptureTypes(CaptureType.REQUEST_CONTENT, CaptureType.RESPONSE_CONTENT);

    // create a new HAR with the label "yahoo.com"

    // open yahoo.com

    // get the HAR data
    Har har = proxy.getHar();

Note: If you're running running tests on a Selenium grid, you will need to customize the Selenium Proxy object created by createSeleniumProxy() to point to the hostname of the machine that your test is running on. You can also run a standalone BrowserMob Proxy instance on a separate machine and configure the Selenium Proxy object to use that proxy.

HTTP Request Manipulation

HTTP request manipulation has changed in 2.1.0+ with LittleProxy. The LittleProxy-based interceptors are easier to use and more reliable. The legacy ProxyServer implementation will not support the new interceptor methods.

2.1.0+ (LittleProxy) interceptors

There are four new methods to support request and response interception in LittleProxy:

  • addRequestFilter
  • addResponseFilter
  • addFirstHttpFilterFactory
  • addLastHttpFilterFactory

For most use cases, including inspecting and modifying requests/responses, addRequestFilter and addResponseFilter will be sufficient. The request and response filters are easy to use:

    proxy.addRequestFilter(new RequestFilter() {
            public HttpResponse filterRequest(HttpRequest request, HttpMessageContents contents, HttpMessageInfo messageInfo) {
                if (messageInfo.getOriginalUri().endsWith("/some-endpoint-to-intercept")) {
                    // retrieve the existing message contents as a String or, for binary contents, as a byte[]
                    String messageContents = contents.getTextContents();

                    // do some manipulation of the contents
                    String newContents = messageContents.replaceAll("original-string", "my-modified-string");

                    // replace the existing content by calling setTextContents() or setBinaryContents()

                // in the request filter, you can return an HttpResponse object to "short-circuit" the request
                return null;

        // responses are equally as simple:
        proxy.addResponseFilter(new ResponseFilter() {
            public void filterResponse(HttpResponse response, HttpMessageContents contents, HttpMessageInfo messageInfo) {
                if (/*...some filtering criteria...*/) {
                    contents.setTextContents("This message body will appear in all responses!");

With Java 8, the syntax is even more concise:

        proxy.addResponseFilter((response, contents, messageInfo) -> {
            if (/*...some filtering criteria...*/) {
                contents.setTextContents("This message body will appear in all responses!");

See the javadoc for the RequestFilter and ResponseFilter classes for more information.

For fine-grained control over the request and response lifecycle, you can add "filter factories" directly using addFirstHttpFilterFactory and addLastHttpFilterFactory (see the examples in the InterceptorTest unit tests).

REST API interceptors with LittleProxy

When running the REST API with LittleProxy enabled, you cannot use the legacy /:port/interceptor/ endpoints. Instead, POST the javascript payload to the new /:port/filter/request and /:port/filter/response endpoints.

Request filters

Javascript request filters have access to the variables request (type io.netty.handler.codec.http.HttpRequest), contents (type net.lightbody.bmp.util.HttpMessageContents), and messageInfo (type net.lightbody.bmp.util.HttpMessageInfo). messageInfo contains additional information about the message, including whether the message is sent over HTTP or HTTPS, as well as the original request received from the client before any changes made by previous filters. If the javascript returns an object of type io.netty.handler.codec.http.HttpResponse, the HTTP request will "short-circuit" and return the response immediately.

Example: Modify User-Agent header

curl -i -X POST -H 'Content-Type: text/plain' -d "request.headers().remove('User-Agent'); request.headers().add('User-Agent', 'My-Custom-User-Agent-String 1.0');" http://localhost:8080/proxy/8081/filter/request
Response filters

Javascript response filters have access to the variables response (type io.netty.handler.codec.http.HttpResponse), contents (type net.lightbody.bmp.util.HttpMessageContents), and messageInfo (type net.lightbody.bmp.util.HttpMessageInfo). As in the request filter, messageInfo contains additional information about the message.

Example: Modify response body

curl -i -X POST -H 'Content-Type: text/plain' -d "contents.setTextContents('<html><body>Response successfully intercepted</body></html>');" http://localhost:8080/proxy/8081/filter/response

Legacy interceptors

If you are using the legacy ProxyServer implementation, you can manipulate the requests like so:

    BrowserMobProxy server = new ProxyServer();
    ((LegacyProxyServer)server).addRequestInterceptor(new RequestInterceptor() {
        public void process(BrowserMobHttpRequest request, Har har) {
            request.getMethod().addHeader("User-Agent", "Bananabot/1.0");

You can also POST a JavaScript payload to /:port/interceptor/request and /:port/interceptor/response using the REST interface. The functions will have a request/response variable, respectively, and a har variable (which may be null if a HAR isn't set up yet). The JavaScript code will be run by Rhino and have access to the same Java API in the example above:

[~]$ curl -X POST -H 'Content-Type: text/plain' -d 'request.getMethod().removeHeaders("User-Agent");' http://localhost:8080/proxy/8081/interceptor/request

Consult the Java API docs for more info.

SSL Support

BrowserMob Proxy 2.1.0+ now supports full MITM: For most users, MITM will work out-of-the-box with default settings. Install the ca-certificate-rsa.cer file in your browser or HTTP client to avoid untrusted certificate warnings. Generally, it is safer to generate your own private key, rather than using the .cer files distributed with BrowserMob Proxy. See the README file in the mitm module for instructions on generating or using your own root certificate and private key with MITM.

Legacy Jetty-based ProxyServer support for MITM: The legacy ProxyServer implementation uses the same ca-certificate-rsa.cer root certificate as the default BrowserMobProxyServer implementation. The previous cybervillainsCA.cer certificate has been removed.

Note: DO NOT permanently install the .cer files distributed with BrowserMob Proxy in users' browsers. They should be used for testing only and must not be used with general web browsing.

If you're doing testing with Selenium, you'll want to make sure that the browser profile that gets set up by Selenium not only has the proxy configured, but also has the CA installed. Unfortunately, there is no API for doing this in Selenium; it must be done manually for each browser and environment.

NodeJS Support

NodeJS bindings for browswermob-proxy are available here. Built-in support for Selenium or use CapserJS-on-PhantomJS or anything else to drive traffic for HAR generation.


When running in stand-alone mode, the proxy loads the default logging configuration from the conf/bmp-logging.yaml file. To increase/decrease the logging level, change the logging entry for net.lightbody.bmp.

DNS Resolution

The BrowserMobProxyServer implementation uses native DNS resolution by default, but supports custom DNS resolution and advanced DNS manipulation. See the ClientUtil class for information on DNS manipulation using the dnsjava resolver.

Building the latest from source

You'll need maven (brew install maven if you're on OS X):

[~]$ mvn -DskipTests

You'll find the standalone BrowserMob Proxy distributable zip at browsermob-dist/target/browsermob-proxy-2.1.5-SNAPSHOT-bin.zip. Unzip the contents and run the browsermob-proxy or browsermob-proxy.bat files in the bin directory.

When you build the latest code from source, you'll have access to the latest snapshot release. To use the SNAPSHOT version in your code, modify the version in your pom: