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  • A new tool by Google is to test and give you the recommendation to improve performance, SEO, security, best practices, and accessibility.

    Google recently launched Lighthouse, an open-source tool to audit your website manually and automatically.

    What metrics are tested by Google Lighthouse?

    There are more than 75 metrics it tests and gives you overall scoring. You might be interested in some of the following popular ones as a site owner, SEO analyst, and webmaster.

    • Performance – time to interactive, latency, speed index, resources optimization, TTFB, asset delivery, scripts execution time, DOM size, etc.
    • SEO – Mobile friendly, meta, crawling, canonical, structure, etc.
    • Best Practices – Image optimization, JS libraries, browser error logging, accessible over HTTPS, known JS vulnerabilities, etc
    • Accessibility  – Page elements, language, ARIA attributes, etc.
    • PWA (Progressive Web Application) – redirect HTTP to HTTPS, response code ok, fast loading on 3G, splash screen, viewport, etc.

    It’s a fantastic tool, and you can use it in multiple ways.

    That’s right – so many ways. If you are a developer, you can use Node.js to run a test programmatically. There are already a few tools in the market powered by Lighthouse that offer continuous site performance monitoring.

    Let’s find out how you run the lighthouse test against your site.

    Start from the easiest one.

    Measure by web.dev

    Google released web.dev a few months back and gained good popularity. Testing online is easy.

    Go to Measure page and enter the URL to run the audit. It will take a few seconds, and you should see the detailed reporting with the overall scoring.

    Results also show the success metrics test for the passed audits and work on those needs attention.

    Don’t spend too much time getting 100. Even Google’s sites don’t score that.

    Consider them as guidelines and try to improve as much you can.

    Note: web.dev emulates a test using a Mobile device, and while writing, I don’t see an option to test using Desktop.


    Do you know Lighthouse is available in your Chrome browser? And, the great news is, you can choose to test using Mobile or Desktop, and it’s available in Developer tools.

    • Open Chrome browser
    • Access your site to test
    • Open Developer tools (Press F12 if using Windows) or right-click on the page and click Inspect.
    • Go to the audits tab.

    As you can see above, you have an option to choose what you want to test. This is great to focus on your goal and get the audit results faster.

    Results look and feel from Chome and web.dev is almost similar.

    But if you look at it carefully, there is one additional metrics group here – Progressive Web App. So another reason to audit using Chrome.


    Lighthouse is available as a Node module. You can install it on your server and use it programmatically or command line. Let’s quickly check out how to install Lighthouse to run some tests.

    Installing Lighthouse on Ubuntu 18.x

    The following, I’ve tested on the DigitalOcean server. Lighthouse requires Node LTS 8.9 or later, and I assume you already have it installed. If not, refer to this Node.js installation guide.

    You will also require a chromium browser to be installed on the server. I covered the installation instruction here.

    Installing Lighthouse is straightforward, as you do other modules.

    • Login to your server
    • Run the following command to install
    npm install -g lighthouse

    I am using -g here, so it gets installed as a global module.

    [email protected]:~# npm install -g lighthouse
    /usr/bin/lighthouse -> /usr/lib/node_modules/lighthouse/lighthouse-cli/index.js
    /usr/bin/chrome-debug -> /usr/lib/node_modules/lighthouse/lighthouse-core/scripts/manual-chrome-launcher.js
    > [email protected] postinstall /usr/lib/node_modules/lighthouse/node_modules/axe-core
    > node build/utils/postinstall.js
    + [email protected]
    added 179 packages from 119 contributors in 10.094s
    [email protected]:~#

    Once installed, run lighthouse command to ensure it has been installed correctly.

    [email protected]:~# lighthouse
    Please provide a url
    Specify --help for available options
    [email protected]:~#

    Good, the lighthouse is ready to run the audit. Let’s try some test options.

    To run a test using a headless browser

    lighthouse URL --chrome-flags="--headless"

    You need to provide an absolute URL, including HTTP or HTTPS.


    [email protected]:~$ lighthouse https://geekflare.com --chrome-flags="--headless"
      ChromeLauncher Waiting for browser. +0ms
      ChromeLauncher Waiting for browser... +1ms
      ChromeLauncher Waiting for browser..... +511ms
      ChromeLauncher Waiting for browser.....✓ +2ms
      status Connecting to browser +176ms
      status Resetting state with about:blank +24ms
      status Benchmarking machine +30ms
      status Initializing… +508ms
      status Loading page & waiting for onload Scripts, CSSUsage, Viewport, ViewportDimensions, ThemeColor, Manifest, RuntimeExceptions, ChromeConsoleMessages, ImageUsage, Accessibility, LinkElements, AnchorsWithNoRelNoopener, AppCacheManifest, Doctype, DOMStats, JSLibraries, OptimizedImages, PasswordInputsWithPreventedPaste, ResponseCompression, TagsBlockingFirstPaint, MetaDescription, FontSize, CrawlableLinks, MetaRobots, Hreflang, EmbeddedContent, Canonical, RobotsTxt +27ms
      status Retrieving in-page: Scripts +2s
      status Retrieving in-page: CSSUsage +0ms
      status Retrieving in-page: Viewport +0ms
      status Retrieving in-page: ViewportDimensions +0ms
      status Retrieving in-page: ThemeColor +0ms
      status Retrieving in-page: Manifest +0ms
      status Retrieving in-page: RuntimeExceptions +0ms
      status Retrieving in-page: ChromeConsoleMessages +0ms
      status Retrieving in-page: ImageUsage +0ms
      status Retrieving in-page: Accessibility +0ms
      status Retrieving in-page: LinkElements +0ms
      status Retrieving in-page: AnchorsWithNoRelNoopener +1ms
      status Retrieving in-page: AppCacheManifest +0ms
      status Retrieving in-page: Doctype +0ms
      status Retrieving in-page: DOMStats +0ms
      status Retrieving in-page: JSLibraries +0ms
      status Retrieving in-page: OptimizedImages +0ms
      status Retrieving in-page: PasswordInputsWithPreventedPaste +0ms
      status Retrieving in-page: ResponseCompression +0ms
      status Retrieving in-page: TagsBlockingFirstPaint +0ms
      status Retrieving in-page: MetaDescription +0ms
      status Retrieving in-page: FontSize +0ms
      status Retrieving in-page: CrawlableLinks +0ms
      status Retrieving in-page: MetaRobots +0ms
      status Retrieving in-page: Hreflang +0ms
      status Retrieving in-page: EmbeddedContent +0ms
      status Retrieving in-page: Canonical +0ms
      status Retrieving in-page: RobotsTxt +0ms
      status Retrieving trace +1ms
      status Retrieving devtoolsLog & network records +110ms
      status Retrieving: Scripts +27ms
      status Retrieving: CSSUsage +53ms
      status Retrieving: Viewport +192ms
      status Retrieving: ViewportDimensions +5ms
      status Retrieving: ThemeColor +13ms
      status Retrieving: Manifest +2ms
      status Retrieving: RuntimeExceptions +295ms
      status Retrieving: ChromeConsoleMessages +1ms
      status Retrieving: ImageUsage +2ms
      status Retrieving: Accessibility +22ms
      status Retrieving: LinkElements +526ms
      status Retrieving: AnchorsWithNoRelNoopener +10ms
      status Retrieving: AppCacheManifest +6ms
      status Retrieving: Doctype +20ms
      status Retrieving: DOMStats +4ms
      status Retrieving: JSLibraries +50ms
      status Retrieving: OptimizedImages +25ms
      status Retrieving: PasswordInputsWithPreventedPaste +234ms
      status Retrieving: ResponseCompression +3ms
      status Retrieving: TagsBlockingFirstPaint +7ms
      status Retrieving: MetaDescription +6ms
      status Retrieving: FontSize +7ms
      status Retrieving: CrawlableLinks +245ms
      status Retrieving: MetaRobots +6ms
      status Retrieving: Hreflang +2ms
      status Retrieving: EmbeddedContent +2ms
      status Retrieving: Canonical +3ms
      status Retrieving: RobotsTxt +6ms
      status Resetting state with about:blank +19ms
      status Loading page & waiting for onload ServiceWorker, Offline, StartUrl +24ms
      status Retrieving in-page: ServiceWorker +59ms
      status Retrieving in-page: Offline +0ms
      status Retrieving in-page: StartUrl +1ms
      status Retrieving devtoolsLog & network records +0ms
      status Retrieving: ServiceWorker +2ms
      status Retrieving: Offline +1ms
      status Retrieving: StartUrl +1ms
      status Resetting state with about:blank +5ms
      status Loading page & waiting for onload HTTPRedirect, HTMLWithoutJavaScript +48ms
      status Retrieving in-page: HTTPRedirect +260ms
      status Retrieving in-page: HTMLWithoutJavaScript +0ms
      status Retrieving devtoolsLog & network records +0ms
      status Retrieving: HTTPRedirect +7ms
      status Retrieving: HTMLWithoutJavaScript +12ms
      status Disconnecting from browser... +7ms
      status Analyzing and running audits... +6ms
      status Evaluating: Uses HTTPS +3ms
      status Evaluating: Redirects HTTP traffic to HTTPS +24ms
      status Evaluating: Registers a service worker that controls page and start_url +1ms
      status Evaluating: Current page responds with a 200 when offline +0ms
      status Evaluating: Has a `<meta name="viewport">` tag with `width` or `initial-scale` +1ms
      status Evaluating: Contains some content when JavaScript is not available +1ms
      status Evaluating: First Contentful Paint +6ms
      status Evaluating: First Meaningful Paint +54ms
      status Evaluating: Page load is fast enough on mobile networks +10ms
      status Evaluating: Speed Index +33ms
      status Evaluating: Screenshot Thumbnails +529ms
      status Evaluating: Final Screenshot +287ms
      status Evaluating: Estimated Input Latency +2ms
      status Evaluating: No browser errors logged to the console +16ms
      status Evaluating: Server response times are low (TTFB) +1ms
      status Evaluating: First CPU Idle +1ms
      status Evaluating: Time to Interactive +30ms
      status Evaluating: User Timing marks and measures +0ms
      status Evaluating: Minimize Critical Requests Depth +2ms
      status Evaluating: Avoid multiple page redirects +3ms
      status Evaluating: Web app manifest meets the installability requirements +2ms
      status Evaluating: Configured for a custom splash screen +1ms
      status Evaluating: Sets an address-bar theme color +0ms
      status Evaluating: Content is sized correctly for the viewport +1ms
      status Evaluating: Displays images with correct aspect ratio +0ms
      status Evaluating: Avoids deprecated APIs +1ms
      status Evaluating: Minimizes main-thread work +0ms
      status Evaluating: JavaScript execution time +11ms
      status Evaluating: Preload key requests +3ms
      status Evaluating: Preconnect to required origins +2ms
      status Evaluating: All text remains visible during webfont loads +2ms
      status Evaluating: Network Requests +1ms
      status Evaluating: Metrics +2ms
      status Evaluating: start_url responds with a 200 when offline +1ms
      status Evaluating: Site works cross-browser +1ms
      status Evaluating: Page transitions don't feel like they block on the network +0ms
      status Evaluating: Each page has a URL +0ms
      status Evaluating: `[aria-*]` attributes match their roles +1ms
      status Evaluating: `[role]`s have all required `[aria-*]` attributes +1ms
      status Evaluating: Elements with `[role]` that require specific children `[role]`s, are present +0ms
      status Evaluating: `[role]`s are contained by their required parent element +1ms
      status Evaluating: `[role]` values are valid +1ms
      status Evaluating: `[aria-*]` attributes have valid values +0ms
      status Evaluating: `[aria-*]` attributes are valid and not misspelled +1ms
      status Evaluating: `<audio>` elements contain a `<track>` element with `[kind="captions"]` +1ms
      status Evaluating: Buttons have an accessible name +1ms
      status Evaluating: The page contains a heading, skip link, or landmark region +1ms
      status Evaluating: Background and foreground colors have a sufficient contrast ratio +1ms
      status Evaluating: `<dl>`'s contain only properly-ordered `<dt>` and `<dd>` groups, `<script>` or `<template>` elements. +1ms
      status Evaluating: Definition list items are wrapped in `<dl>` elements +0ms
      status Evaluating: Document has a `<title>` element +1ms
      status Evaluating: `[id]` attributes on the page are unique +1ms
      status Evaluating: `<frame>` or `<iframe>` elements have a title +1ms
      status Evaluating: `<html>` element has a `[lang]` attribute +0ms
      status Evaluating: `<html>` element has a valid value for its `[lang]` attribute +1ms
      status Evaluating: Image elements have `[alt]` attributes +1ms
      status Evaluating: `<input type="image">` elements have `[alt]` text +1ms
      status Evaluating: Form elements have associated labels +0ms
      status Evaluating: Presentational `<table>` elements avoid using `<th>`, `<caption>` or the `[summary]` attribute. +1ms
      status Evaluating: Links have a discernible name +1ms
      status Evaluating: Lists contain only `<li>` elements and script supporting elements (`<script>` and `<template>`). +1ms
      status Evaluating: List items (`<li>`) are contained within `<ul>` or `<ol>` parent elements +1ms
      status Evaluating: The document does not use `<meta http-equiv="refresh">` +0ms
      status Evaluating: `[user-scalable="no"]` is not used in the `<meta name="viewport">` element and the `[maximum-scale]` attribute is not less than 5. +1ms
      status Evaluating: `<object>` elements have `[alt]` text +1ms
      status Evaluating: No element has a `[tabindex]` value greater than 0 +1ms
      status Evaluating: Cells in a `<table>` element that use the `[headers]` attribute only refer to other cells of that same table. +1ms
      status Evaluating: `<th>` elements and elements with `[role="columnheader"/"rowheader"]` have data cells they describe. +0ms
      status Evaluating: `[lang]` attributes have a valid value +1ms
      status Evaluating: `<video>` elements contain a `<track>` element with `[kind="captions"]` +1ms
      status Evaluating: `<video>` elements contain a `<track>` element with `[kind="description"]` +1ms
      status Evaluating: `[accesskey]` values are unique +1ms
      status Evaluating: Custom controls have associated labels +0ms
      status Evaluating: Custom controls have ARIA roles +1ms
      status Evaluating: User focus is not accidentally trapped in a region +0ms
      status Evaluating: Interactive controls are keyboard focusable +0ms
      status Evaluating: Headings don't skip levels +0ms
      status Evaluating: Interactive elements indicate their purpose and state +1ms
      status Evaluating: The page has a logical tab order +0ms
      status Evaluating: The user's focus is directed to new content added to the page +1ms
      status Evaluating: Offscreen content is hidden from assistive technology +0ms
      status Evaluating: HTML5 landmark elements are used to improve navigation +0ms
      status Evaluating: Visual order on the page follows DOM order +0ms
      status Evaluating: Uses efficient cache policy on static assets +1ms
      status Evaluating: Avoids enormous network payloads +3ms
      status Evaluating: Defer offscreen images +1ms
      status Evaluating: Eliminate render-blocking resources +12ms
      status Evaluating: Minify CSS +28ms
      status Evaluating: Minify JavaScript +64ms
      status Evaluating: Defer unused CSS +69ms
      status Evaluating: Serve images in next-gen formats +12ms
      status Evaluating: Efficiently encode images +11ms
      status Evaluating: Enable text compression +6ms
      status Evaluating: Properly size images +6ms
      status Evaluating: Use video formats for animated content +7ms
      status Evaluating: Avoids Application Cache +11ms
      status Evaluating: Page has the HTML doctype +0ms
      status Evaluating: Avoids an excessive DOM size +1ms
      status Evaluating: Links to cross-origin destinations are safe +2ms
      status Evaluating: Avoids requesting the geolocation permission on page load +1ms
      status Evaluating: Avoids `document.write()` +0ms
      status Evaluating: Avoids front-end JavaScript libraries with known security vulnerabilities +0ms
      status Evaluating: Detected JavaScript libraries +9ms
      status Evaluating: Avoids requesting the notification permission on page load +1ms
      status Evaluating: Allows users to paste into password fields +0ms
      status Evaluating: Uses HTTP/2 for its own resources +0ms
      status Evaluating: Uses passive listeners to improve scrolling performance +1ms
      status Evaluating: Document has a meta description +0ms
      status Evaluating: Page has successful HTTP status code +1ms
      status Evaluating: Document uses legible font sizes +5ms
      status Evaluating: Links have descriptive text +1ms
      status Evaluating: Page isn’t blocked from indexing +1ms
      status Evaluating: robots.txt is valid +2ms
      status Evaluating: Document has a valid `hreflang` +1ms
      status Evaluating: Document avoids plugins +1ms
      status Evaluating: Document has a valid `rel=canonical` +0ms
      status Evaluating: Page is mobile friendly +1ms
      status Evaluating: Structured data is valid +0ms
      status Generating results... +0ms
      ChromeLauncher Killing Chrome instance 7098 +59ms
      Printer html output written to /home/chandan/geekflare.com_2019-01-20_19-29-35.report.html +46ms
      CLI Protip: Run lighthouse with `--view` to immediately open the HTML report in your browser +1ms

    In the second last line, you can see it has printed the path to find the report. By default, it will generate a report in HTML format, which you can view either by downloading on your PC or serving it through some web server.

    But, what if you have to generate a report in JSON format?

    It’s doable as the following.

    lighthouse URL --chrome-flags="--headless" --output json --output-path URL.json

    By using Lighthouse CLI, you are in full control to use it the way you want it. I would strongly recommend checking out the GitHub repository to learn more about using CLI or programmatically.


    Google Lighthouse looks like a promising tool to perform a continuity test to improve site performance and usability. If you are using WordPress and looking to make your site load faster, check out Rocket.