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2.4.1 • Public • Published


Louis is a gulp task that is used to analyze the performance of a website against a performance budget.

npm version



There are many definitions of the performance budget on the web, my favourite is from Zachary Brady.

A performance budget provides values against which design, development, content, or any aspect of a site that may affect performance, can be made.

The aim of the plugin is to analyze the performance of the website against a performance bugdet. There are various metrics against which we can set a performance budget e.g. number of requests, imageSize etc.

Getting started


1. Usage

2. Example

3. Output

4. Options

5. Performance Budget Options

6. Change log

Getting Started


$ npm install --save-dev gulp-louis
import louis = require('gulp-louis');
gulp.task('louis', function(done) {
    timeout: 60,
    viewport: '1280x1024',
    engine: 'webkit',
    userAgent: 'Chrome/37.0.2062.120',
    noExternals: false,
    performanceBudget: {
      requests: 2,
      medianLatency: 10,
      slowestResponse: 1000
  }, done);
gulp.task('default', ['louis']);


Example 1 (with specified url)

  url: 'http://localhost:8000/',
  timeout: 200,
  performanceBudget: {
    requests: 10,
    domComplete: 3000

Example 2 (without url) This will launch a server and look for an index.html in the same folder as the gulpfile.js, then it will analyze the performance of this website.

  timeout: 10,
  performanceBudget: {
    requests: 10,
    headersSize: 200


Output with specified performance budget


Output without specified performance budget



All options are optional

  • url url of the website to be analyzed, if it is not specified Louis will launch a server and load the index.html if this exist on the same directory as the gulpfile.js
  • timeout timeout for the run (defaults to 15 seconds)
  • viewport dimensions ('1280x1024' is the default)
  • engine webkit or gecko (webkit is default)
  • userAgent default is Chrome/37.0.2062.120
  • noExternals true or false, default is false, block requests to 3rd party domains
  • outputFileName name of file to write the results, default is "results.json"
  • performanceBudget object with metrics, see below
  • proxy specifies the (optional) proxy server to use

Performance Budget Options

The performance budget option can contain some or all of these values:

requests, gzipRequests, postRequests, httpsRequests, notFound, bodySize, contentLength, httpTrafficCompleted, timeToFirstByte, timeToLastByte, ajaxRequests, htmlCount, htmlSize, cssCount, cssSize, jsCount, jsSize, jsonCount, jsonSize, imageCount, imageSize, videoCount, videoSize, webfontCount, webfontSize, base64Count, base64Size, otherCount, otherSize, cacheHits, cacheMisses, cachePasses, cachingNotSpecified, cachingTooShort, cachingDisabled, oldCachingHeaders, consoleMessages, cookiesSent, cookiesRecv, domainsWithCookies, documentCookiesLength, documentCookiesCount, documentHeight, commentsSize, whiteSpacesSize, DOMelementsCount, DOMelementMaxDepth, nodesWithInlineCSS, imagesScaledDown, imagesWithoutDimensions, DOMidDuplicated, hiddenContentSize, DOMmutationsInsertsv, DOMmutationsRemoves, DOMmutationsAttributes, DOMqueries, DOMqueriesWithoutResults, DOMqueriesById, DOMqueriesByClassName, DOMqueriesByTagName, DOMqueriesByQuerySelectorAll , DOMinserts, DOMqueriesDuplicated, DOMqueriesAvoidable, domains, maxRequestsPerDomain, medianRequestsPerDomain, eventsBound, eventsDispatched, globalVariables, globalVariablesFalsy, headersCount, headersSentCount, headersRecvCount, headersSize, headersSentSize, headersRecvSize, headersBiggerThanContent, jQueryVersion, jQueryVersionsLoaded, jQueryOnDOMReadyFunctions, jQueryWindowOnLoadFunctions, jQuerySizzleCalls, jQueryEventTriggers, jQueryDOMReads, jQueryDOMWrites, jQueryDOMWriteReadSwitches, documentWriteCalls, evalCalls, jsErrors, closedConnections, localStorageEntries, redirects, redirectsTime, repaints, firstPaint, requestsToDomContentLoaded, requestsToDomComplete, assetsNotGzipped, assetsWithQueryString, assetsWithCookies, smallImages, smallCssFiles, smallJsFiles, multipleRequests, timeToFirstCss, timeToFirstJs, timeToFirstImage, domInteractive, domContentLoaded, domContentLoadedEnd, domComplete, timeBackend, timeFrontend, statusCodesTrail, windowAlerts, windowConfirms, windowPrompts, bodyHTMLSize, iframesCount, smallestResponse, biggestResponse, fastestResponse, slowestResponse, smallestLatency, biggestLatency, medianResponse, medianLatency


performanceBudget = {
  cssSize: 200
  jsSize: 2000
  consoleMessages: 0
  imageSize: 5000
  domContentLoaded: 2000
  smallestLatency: 1000

Change log

[2.3.2] - 2018-03-16

  • Fix / appended to outputFile causing throw in unix systems

[2.3.1] - 2018-02-28

  • Update dependencies

[2.3.0] - 2016-10-07

  • Added proxy-option

[2.2.1] - 2016-09-29

  • Update dependencies

[2.2.0] - 2016-09-29

  • Add outputFilename-option

[2.1.1] - 2016-09-16

  • Update dependencies

[2.1.0] - 2016-09-15

  • Change the results.json to a file with the same of tested domain.

[2.0.0] - 2016-08-29

  • Run phantomas from local path
  • Update depedencies

[1.1.0] - 2016-08-19

  • Fix phantomas path

[1.0.14] - 2015-11-23

Bug Fixes

  • Fix path to phantomas command …

  • Add missing gulp-connect dependency

  • Change "main" script to "louis.js"

[1.0.10] - 2015-02-21

[1.0.9] - 2015-02-21

[1.0.8] - 2015-02-20

[1.0.7] - 2015-02-17

[1.0.0] - 2015-02-16


Released under the MIT license.


npm i gulp-louis

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