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PhantomJS-based web performance metrics collector


PhantomJS-based modular web performance metrics collector. And why phantomas? Well, because :)

npm install --global phantomas

This will install the latest version of PhantomJS and add a symlink called phantomas (pointing to ./bin/phantomas.js) to your system's PATH

You may need to install libfontconfig by running sudo apt-get install libfontconfig1.

To get the latest development version of phantomas (and install all required dependencies):

git clone
npm install

Please refer to /

phantomas is written in JavaScript, but you can experience it in different languages as well ;)

pip install phantomas
  • modular approach - each metric is generated by a separate "module"
  • phantomas "core" acts as an events emitter that each module can hook into
  • in-depth metrics such as: number of events bound via jQuery, calls to window.writeor complex and duplicated CSS selectors (via analyze-css)
  • JSON and CSV as available output formats for easy integration with automated reporting / monitoring tools
  • easy integration with Continuous Integration tools via TAP format and assertions handling
  • metrics can be sent via StatsD or stored in elasticsearch
  • easy integration with other nodejs projects via CommonJS module (see API docs)
  • metrics can be emitted from JavaScript code of the page phantomas is run against (thanks to helper functions available in window.__phantomas)
  • device profiles allow phantomas to emulate mobile or tablet (by setting a proper user agent and viewport)
  • ability to run phantomas using WebKit (PhantomJS) or Gecko (SlimerJS) engine (experimental)

All the contributors

phantomas comes as both command line tool and CommonJS module (see API docs) that you can use in your nodejs projects.

phantomas --verbose

You can measure the performance of your site without requests to 3rd party domains (but allowing CDN that serves your static assets):

phantomas --verbose --no-externals --allow-domain
  • --reporter=[json|csv|tap|plain|statsd|elasticsearch|cloudwatch] results reporter aka format (plain is the default one)
  • --timeout=[seconds] timeout for phantomas run (defaults to 15 seconds)
  • --viewport=[width]x[height] phantomJS viewport dimensions (1280x1024 is the default)
  • --verbose writes debug messages to the console
  • --debug run PhantomJS in debug mode
  • --engine select engine used to run the phantomas [webkit|gecko]
  • --colors forces ANSI colors even when output is piped (e,g. via less -r)
  • --silent don't write anything to the console
  • --progress shows page loading progress bar (disables verbose mode)
  • --log=[log file] log to a given file
  • --modules=[moduleOne],[moduleTwo] run only selected modules
  • --include-dirs=[dirOne],[dirTwo] load modules from specified directories
  • --skip-modules=[moduleOne],[moduleTwo] skip selected modules
  • --user-agent='Custom user agent' provide a custom user agent (will default to something similar to phantomas/0.6.0 (PhantomJS/1.9.0; linux 64bit))
  • --config=[JSON/YAML config file] uses JSON or YAML-formatted config file to set parameters
  • --cookie='bar=foo;domain=url' document.cookie formatted string for setting a single cookie
  • --cookies-file=[JAR file] specifies the file name to store the persistent Cookies
  • --no-externals block requests to 3rd party domains
  • --allow-domain=[domain],[domain] allow requests to given domain(s) - aka whitelist
  • --block-domain=[domain],[domain] disallow requests to given domain(s) - aka blacklist
  • --auth-user sets the user name used for HTTP authentication
  • --auth-pass sets the password used for HTTP authentication
  • --disable-js disable JavaScript on the page that will be loaded
  • --analyze-css emit in-depth CSS metrics experimental
  • --film-strip register film strip when page is loading experimental
  • --film-strip-dir=[dir path] folder path to output film strip (default is ./filmstrip directory)
  • --film-strip-prefix film strip files name prefix (defaults to screenshot)
  • --page-source save page source to file experimental
  • --page-source-dir=[dir path] folder path to output page source (default is ./html directory) experimental
  • --assert-[metric-name]=value assert that given metric should be less or equal the value
  • --screenshot=[file name] render fully loaded page to a given file
  • --har=[file name] save HAR to a given file
  • --wait-for-event=[phantomas event name] wait for a given phantomas event before generating a report, timeout setting still applies (e.g. --wait-for-event "done")
  • --wait-for-selector=[CSS selector] wait for an element matching given CSS selector before generating a report, timeout setting still applies (e.g. --wait-for-selector "body.loaded")
  • --stop-at-onload stop phantomas immediately after onload event
  • --scroll scroll down the page when it''s loaded
  • --post-load-delay=[seconds] wait X seconds before generating a report, timeout setting still applies
  • --ignore-ssl-errors ignores SSL errors, such as expired or self-signed certificate errors
  • --ssl-protocol sets the SSL protocol for secure connections [sslv3|sslv2|tlsv1|any]
  • --proxy=[host:port] specifies the proxy server to use
  • --proxy-auth=[username:password] specifies the authentication information for the proxy
  • --proxy-type=[http|socks5|none] specifies the type of the proxy server (default is http)
  • --phone force viewport and user agent of a mobile phone
  • --tablet force viewport and user agent of a tablet
  • --spy-eval report calls to eval()

Simply provide --runs option:

phantomas --verbose --runs 5

Only plain (the default one) and json reporters are currently supported in multiple runs mode.

Current number of metrics: 135


  • ms for time
  • bytes for size

Due to PhantomJS issue #10156 body size related metrics are not reliable

  • requests: total number of HTTP requests made
  • gzipRequests: number of gzipped HTTP responses
  • postRequests: number of POST requests
  • httpsRequests: number of HTTPS requests
  • notFound: number of HTTP 404 responses
  • timeToFirstByte: time it took to receive the first byte of the first response (that was not a redirect)
  • timeToLastByte: time it took to receive the last byte of the first response (that was not a redirect)
  • bodySize: size of the content of all responses
  • contentLength: size of the content of all responses (based on Content-Length header)
  • httpTrafficCompleted: time it took to receive the last byte of the last HTTP response
  • ajaxRequests: number of AJAX requests

Due to PhantomJS issue #10156 body size related metrics are not reliable

  • htmlCount: number of HTML responses
  • htmlSize: size of HTML responses
  • cssCount: number of CSS responses
  • cssSize: size of CSS responses
  • jsCount: number of JS responses
  • jsSize: size of JS responses
  • jsonCount: number of JSON responses
  • jsonSize: size of JSON responses
  • imageCount: number of image responses
  • imageSize: size of image responses
  • webfontCount: number of web font responses
  • webfontSize: size of web font responses
  • videoCount: number of video responses
  • videoSize: size of video responses
  • base64Count: number of base64 encoded "responses" (no HTTP request was actually made)
  • base64Size: size of base64 encoded "responses"
  • otherCount: number of other responses
  • otherSize: size of other responses

Metrics are calculated based on Age and X-Cache headers added by Varnish / Squid servers

  • cacheHits: number of cache hits
  • cacheMisses: number of cache misses
  • cachePasses: number of cache passes
  • headersCount: number of requests and responses headers
  • headersSentCount: number of headers sent in requests
  • headersRecvCount: number of headers received in responses
  • headersSize: size of all headers
  • headersSentSize: size of sent headers
  • headersRecvSize: size of received headers
  • headersBiggerThanContent: number of responses with headers part bigger than the response body
  • domains: number of domains used to fetch the page
  • maxRequestsPerDomain: maximum number of requests fetched from a single domain
  • medianRequestsPerDomain: median of requests fetched from each domain
  • cookiesSent: length of cookies sent in HTTP requests
  • cookiesRecv: length of cookies received in HTTP responses
  • domainsWithCookies: number of domains with cookies set
  • documentCookiesLength: length of document.cookie
  • documentCookiesCount: number of cookies in document.cookie

Metrics listed below are generated after the full page load

  • globalVariables: number of JS globals variables
  • globalVariablesFalsy: number of JS global variables that cast to false
  • bodyHTMLSize: the size of body tag content (document.body.innerHTML.length)
  • commentsSize: the size of HTML comments on the page
  • whiteSpacesSize: the size of text nodes with whitespaces only
  • DOMelementsCount: total number of HTML element nodes
  • DOMelementMaxDepth: maximum level on nesting of HTML element node
  • DOMidDuplicated: number of duplicated IDs found in DOM
  • iframesCount: number of iframe nodes
  • nodesWithInlineCSS: number of nodes with inline CSS styling (with style attribute)
  • imagesScaledDown: number of nodes that have images scaled down in HTML
  • imagesWithoutDimensions: number of <img> nodes without both width and height attribute
  • hiddenContentSize: the size of content of hidden elements on the page (with CSS display: none)
  • hiddenImages: number of hidden images that can be lazy-loaded
  • DOMqueries: the sum of all four metrics below
  • DOMqueriesWithoutResults: number of DOM queries that returned nothing
  • DOMqueriesById: number of document.getElementById calls
  • DOMqueriesByClassName: number of document.getElementsByClassName calls
  • DOMqueriesByTagName: number of document.getElementsByTagName calls
  • DOMqueriesByQuerySelectorAll: number of document.querySelectorAll calls
  • DOMinserts: number of DOM nodes inserts
  • DOMqueriesDuplicated: number of DOM queries called more than once
  • DOMqueriesAvoidable: number of repeated uses of a duplicated query

These metrics are only available when running phantomas using Gecko engine (--engine=gecko)

  • DOMmutationsInserts: number of node inserts
  • DOMmutationsRemoves: number of node removes
  • DOMmutationsAttributes: number of DOM nodes attributes changes
  • eventsBound: number of EventTarget.addEventListener calls
  • eventsDispatched: number of EventTarget.dispatchEvent calls
  • eventsScrollBound: number of scroll event bounds to window or document

Times below are relative to responseEnd entry in NavigationTiming (represented by timeToLastByte metric). See NavigationTiming spec for more information.

  • domInteractive: time it took to parse the HTML and construct the DOM
  • domContentLoaded: time it took to construct both DOM and CSSOM, no stylesheets are blocking JavaScript execution (i.e. onDOMReady)
  • domContentLoadedEnd: time it took to finish handling of onDOMReady event experimental
  • domComplete: time it took to load all page resources, the loading spinner has stopped spinning
  • timeBackend: time to the first byte compared to the total loading time (in %)
  • timeFrontend: time to window on load compared to the total loading time (in %)

These metrics are only available when running phantomas using Gecko engine (--engine=gecko)

  • repaints: number of repaints of the current document
  • firstPaint: time it took to perform the first paint (time is relative to responseEnd event)

Time is total duration, from the start of the request to the receipt of the final byte in the response. Latency is the time to load the first byte in the response.

Includes HTTP 200 responses only

  • smallestResponse: the size of the smallest response
  • biggestResponse: the size of the biggest response
  • fastestResponse: the time to the last byte of the fastest response
  • slowestResponse: the time to the last byte of the slowest response
  • smallestLatency: the time to the first byte of the fastest response
  • biggestLatency: the time to the first byte of the slowest response
  • medianResponse: median value of time to the last byte for all responses
  • medianLatency: median value of time to the first byte for all responses
  • requestsToFirstPaint: number of HTTP requests it took to make the first paint
  • domainsToFirstPaint: number of domains used to make the first paint
  • requestsToDomContentLoaded: number of HTTP requests it took to make the page reach DomContentLoaded state
  • domainsToDomContentLoaded: number of domains used to make the page reach DomContentLoaded state
  • requestsToDomComplete: number of HTTP requests it took to make the page reach DomComplete state
  • domainsToDomComplete: number of domains used to make the page reach DomComplete state

Monitors the use of Connection: close and Keep-Alive

  • closedConnections: number of requests not keeping the connection alive and slowing down the next request
  • localStorageEntries: number of entries in local storage

Requires jQuery 1.8.0+

  • jQueryVersion: version of jQuery framework (if loaded)
  • jQueryVersionsLoaded: number of loaded jQuery "instances" (even in the same version)
  • jQueryOnDOMReadyFunctions: number of functions bound to onDOMReady event
  • jQueryWindowOnLoadFunctions: number of functions bound to windowOnLoad event
  • jQuerySizzleCalls: number of calls to Sizzle (including those that will be resolved using querySelectorAll)
  • jQueryEventTriggers: number of jQuery event triggers
  • jQueryDOMReads: number of DOM read operations
  • jQueryDOMWrites: number of DOM write operations
  • jQueryDOMWriteReadSwitches: number of read operations that follow a series of write operations (will cause repaint and can cause reflow)
  • assetsNotGzipped: static assets that were not gzipped
  • assetsWithQueryString: static assets requested with query string (e.g. ?foo) in URL
  • assetsWithCookies: number of static assets requested from domains with cookie set
  • smallImages: images smaller than 2 KiB that can be base64 encoded
  • smallCssFiles: number of CSS assets smaller than 2 KiB that can be inlined or merged
  • smallJsFiles: number of JS assets smaller than 2 KiB that can be inlined or merged
  • multipleRequests: number of static assets that are requested more than once
  • cachingNotSpecified: responses with no caching header sent (either Cache-Control or Expires)
  • cachingTooShort: responses with too short (less than a week) caching time
  • cachingDisabled: responses with caching disabled (max-age=0)
  • oldCachingHeaders: responses with old, HTTP 1.0 caching headers (Expires and Pragma)
  • timeToFirstCss: time it took to receive the last byte of the first CSS
  • timeToFirstJs: time it took to receive the last byte of the first JS
  • timeToFirstImage: time it took to receive the last byte of the first image
  • redirects: number of HTTP redirects (either 301, 302 or 303)
  • redirectsTime: time it took to send and receive redirects
  • documentWriteCalls: number of calls to either document.write or document.writeln
  • evalCalls: number of calls to eval (either direct or via setTimeout / setInterval)

Error message and backtrace will be emitted as offenders

  • jsErrors: number of JavaScript errors
  • windowAlerts: number of calls to alert
  • windowConfirms: number of calls to confirm
  • windowPrompts: number of calls to prompt
  • consoleMessages: number of calls to console.* functions

Analyzes bits of data pertaining to the main request only

  • statusCodesTrail: comma-separated list of HTTP status codes that main request followed through (could contain a single element if the main request is a terminal one)
  • lazyLoadableImagesBelowTheFold: number of images displayed below the fold that can be lazy-loaded

The following metrics are emitted only when certain options are passed to phantomas

  • blockedRequests: number of requests blocked due to domain filtering (emitted only when in --no-externals / --block-domain mode)

This is an experimental feature. Use --analyze-css option to enable it.

Take a look at analyze-css README for the full list of metrics.

  • cssParsingErrors: number of CSS files (or embeded CSS) that failed to be parse by analyze-css

phantomas provides a number of reporters that can format the run results and send them to various tools. Use --reporter (or -R shortcut) option to use one.

Results can be emitted as TAP, CSV and JSON. plain format is most useful for human beings :)

Formatters can be provided with colon separated list of options:

$ phantomas -R csv:no-header:timestamp

This will omit CSV headers row and add current timestamp as the first column, so you can append the results line to a growing file.

  • no-header - omit CSV header
  • timestamp - add the current timestamp as the first column
  • url - add the URL as the first column
  • <host>:<port>:<index>:<type> - shorthand for --elasticsearch-* options
  • pretty - emits pretty printed JSON
  • no-color - disable ANSI colors
  • <host>:<port>:<prefix> - shorthand for --statsd-host, --statsd-port and --statsd-prefix (you don't need to provide all three options)
  • no-skip - don't print out metrics that were skipped
  • <host>:<port>:<prefix> - shorthand for --statsd-host, --statsd-port and --statsd-prefix (you don't need to provide all three options)
  • <accessKeyId>:<secretKey>:<region>:<apiVersion>:<namespace> - shorthand for --aws-access-key-id, --aws-secret-key, --aws-region, --aws-cloudwatch-api-version and --aws-cloudwatch-namespace (only AccessKeyId and SecretKey are required)

Metrics from phantomas run can be sent directly to StatsD and then graphed using graphite, graphene or any other tool of your choice. For instance:

$ phantomas -R statsd --statsd-host --statsd-port 8125 --statsd-prefix 'myApp.mainPage.'


$ phantomas -R

will sent metrics to StatsD running on and prefix them with 'myApp.mainPage'.

Metrics from phantomas run can be outputted directly in Elasticsearch :

  • --elasticsearch-host=[ip] Elasticsearch instance ip (default :
  • --elasticsearch-port=[port] Elasticsearch instance port (default : 9200)
  • --elasticsearch-index=[index_name] Name of the index to use
  • --elasticsearch-type=[type_name] Name of the document type to use

Or by using reporter options (<host>:<port>:<index>:<type>):

$ phantomas -R

Note: as <port> option was skipped a default value will be used (9200).

  • --aws-access-key-id : a valid aws access key id with CloudWatch rights
  • --aws-secret-key : a corresponding secret key
  • --aws-region us-east-1 : aws server region (default to 'us-east-1')
  • --aws-cloudwatch-api-version : aws CloudWatch Api version (default to 'latest')
  • --aws-cloudwatch-namespace : CloudWatch metric namespace where all the metrics will be saved (default to phantomas)

Or by using reporter options (<AWSAccessKeyId>:<AWSSecretKey>:<AWSRegion>:<CloudWatchApiVersion>:<CloudWatchNameSpace>)

phantomas can be run using PhantomJS 2.1.x (WebKit-powered headless browser) or SlimerJS (Gecko-based non headless browser, run using xfvb).

PhantomJS 2.1.x is a default engine.

You can choose the engine by using either:

  • cli option: --engine=[webkit|gecko] or --webkit / --gecko
  • PHANTOMAS_ENGINE environmental variable: e.g. PHANTOMAS_ENGINE=gecko

Please note that support for SlimerJS is experimental at this point.

All required binaries are installed by npm. No extra work needed here :)

In order to use SlimerJS install the following Debian/Ubuntu packages:

sudo aptitude install xvfb libasound2 libgtk2.0-0

You can load your own, custom phantomas modules using --include-dirs option:

phantomas --include-dirs /my/path/to/custom/modules/ --url

/my/path/to/custom/modules/ directory should contain custom modules, each in its own directory, e.g. /my/path/to/custom/modules/fooBar/fooBar.js.

Introductions to phantomas and use cases:

Use grunt to automate daily dev tasks, including your's application web performance, via these great tools: