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You can use these custom commands for the JavaScript Executor, in conjunction with the Extended debugging feature, to control networking capabilities for your tests, and to generate custom logs. 

Extended Debugging Required

You must have Extended Debugging enabled and run your tests on Chrome browsers to use these commands.

Beta Feature

This feature is currently in Beta and some commands might not work as expected. Please test the results of these commands under non-critical conditions before deploying to critical production situations.

Network Commands

Intercept Network Requests

Allows modifying any request made by the browser. You can blacklist, modify, or redirect these as required for your tests. For example, you can:

  • Blacklist requests to 3rd party vendors
  • Modify requests to REST API (Mock REST API response)
  • Redirect certain parts of the app 
  • Insert/change headers
JavaScript Executor CommandRequest ParametersSample Code

sauce:intercept + redirect

url: a string that matches an outgoing request URL. Wildcards are supported, for example* would match all v1 rest API requests.

redirect is a string representing an absolute URL where the original request is redirected. In the example, this is ""

driver.execute_script('sauce:intercept', {
    "url": "",
    "redirect": ""

sauce:intercept + respond

url: a string that matches an outgoing request URL. Wildcards are supported, for example* would match all v1 rest API requests.

respond: an object that represents the response to send when the requested URL is intercepted. There are three options:

    • statusCode: number representing the request status (200)
    • headers: list of key/value pairs that is set as header variables, for example Cookie: "foo=bar"
    • rawResponse: actual response payload as a string
driver.execute_script('sauce:intercept', {
	url: '',
        response: {
            headers: {
                'x-custom-header': 'foobar'
            body: [{
                title: 'Hello',
                order: 1,
                completed: false,
                url: ""
sauce:intercept+ error

url: a string that matches an outgoing request URL. Wildcards are supported, for example* would match all v1 rest API requests.

error: error values are:

  • 'Failed'
  • 'Aborted'
  • 'TimedOut'
  • 'AccessDenied'
  • 'ConnectionClosed'
  • 'ConnectionReset' 
  • 'ConnectionRefused'
  • 'ConnectionAborted'
  • 'ConnectionFailed'
  • 'NameNotResolved'
  • 'InternetDisconnected'
  • 'AddressUnreachable'
driver.execute_script('sauce:intercept', {
	url: '',
    error: 'Failed'}


Python example
driver.execute_script('sauce:intercept', {
    "url": "",
    "redirect": ""
# or
driver.execute_script('sauce:intercept', {
    "url": "",
    "respond": {
        "statusCode": 200,
        "headers": {
            "etag": 3244224432,
            "Cookie: "foo=bar",
        "rawResponse": "{\"username\":\"..."

Throttle Network Capabilities

With network conditioning you can test your site on a variety of network connections, including Edge, 3G, and even offline. You can throttle the data throughput, including the maximum download and upload throughput, and use latency manipulation to enforce a minimum delay in connection round-trip time (RTT).

JavaScript Executor CommandRequest ParametersExample

conditioncan be a string or object representing the network condition of the browser.


Strings should correspond to the predefined profile names in this table.

Profile NameDownload Speed (kb/s)Upload Speed (kb/s)Round Trip Time (ms)
Regular 2G25050300
Good 2G450150150
Regular 3G750250100
Good 3G1Mb/s75040
Regular 4G4Mb/s3Mb/s20ms
objectWith objects you can create custom network conditions. You must define the download speed, upload speed, and latency for the custom condition, as shown in the example.
driver.execute_script('sauce:throttle', {
	"condition": "GPRS"
# or
driver.execute_script('sauce:throttle', {
	"condition": {
		"download": 1000,
		"upload": 500,
		"latency": 40

Custom Log Types

Network Timing Log

The Sauce Labs timing log receives page metrics for network timings as defined by the PerformanceTiming property. All timings are relative to navigationStart, since the absolute timings described for the property are not useful for testing purposes.

JavaScript Executor CommandResponse
Sample response
    "navigationStart": 0
    "unloadEventStart": -1
    "unloadEventEnd": -1
    "redirectStart": 0
    "redirectEnd": 312
    "fetchStart": 312
    "domainLookupStart": 312
    "domainLookupEnd": 312
    "connectStart": 312
    "connectEnd": 312
    "secureConnectionStart": -1
    "requestStart": 39
    "responseStart": 309
    "responseEnd": 312
    "domLoading": 316
    "domInteractive": 359
    "domContentLoadedEventStart": 560
    "domContentLoadedEventEnd": 560
    "domComplete": 622
    "loadEventStart": 622
    "loadEventEnd": 622

Application Metrics Log

The Sauce Labs metric log receives application-related metrics. As with the timing log, all metrics are relative to the page load time.

JavaScript ExecutorResponse
Sample response
    "timestamp": 35037.202627,
    "audioHandlers": 0,
    "documents": 3,
    "frames": 2,
    "jsEventListeners": 63,
    "layoutObjects": 435,
    "nodes": 506,
    "resources": 11,
    "layoutCount": 2,
    "recalcStyleCount": 5,
    "layoutDuration": 0.0860430000029737,
    "recalcStyleDuration": 0.00374899999587797,
    "scriptDuration": 0.0770069999925909,
    "taskDuration": 0.297364000020025,
    "jsHeapUsedSize": 6295344,
    "jsHeapTotalSize": 10891264,
    "firstMeaningfulPaint": 35036.03356,
    "domContentLoaded": 35036.122972,
    "navigationStart": 35035.833805

Network Log

The Sauce Labs network log receives comprehensive information on all network requests being made by the page currently open in the browser.

JavaScript Executor CommandResponse
Sample response
    "url": "",
    "requests": [{
        "url": "",
        "statusCode": 200,
        "method": "GET",
        "requestHeaders": {
        "responseHeaders": {
        "timing": {
            "blocked": -1,
            "connect": -1,
            "dns": -1,
            "receive": 0,
            "send": 0,
            "ssl": -1,
            "wait": 0
    }, {
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