Implementing Lighthouse Performance Audits using Node CLI

Implementing Lighthouse Performance Audits using Node CLI

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    There is a convenient way to produce Lighthouse Audits through the Node Command Line Interface or Node CLI. The reports generated may be with or without customization.

    The CLI live documentation can and instructions to run can be found on the main Github page > https://github.com/GoogleChrome/lighthouse#output-examples

    lighthouse performance audit

    Getting Started

    1. If you are trying to use the CLI, then you should install the lighthouse remotely using the code:

    npm install lighthouse

    Or you can install globally using

    npm install -g lighthouse

    Note: Lighthouse requires Node 14 LTS (14.x) or later.

    1. You can now Run the lighthouse report on any URL by the following line

    lighthouse https://thatware.co/

    Lighthouse will start gathering all performance related data to check in the reports.

    The final report will be generated by default in C:/ drive. In this case it was generated in the following path.

    C:\Users\SEO\thatware.co_2022-06-01_19-07-56.report.html

    Final Report

    Here’s a sample Report generated for ThatWare:

    Notes on Error Reporting

    The first time you run the CLI you will be prompted with a message asking you if Lighthouse can anonymously report runtime exceptions. The Lighthouse team uses this information to detect new bugs and avoid regressions. Opting out will not affect your ability to use Lighthouse in any way.

    Setting up Node JS environment

    To use different npm packages and run JavaScript applications, you must first set up a Node.js environment. Here’s how to install Node.js and npm on your system and a list of all the npm packages you need to run Lighthouse audits using the Node CLI, including Puppeteer and Lighthouse:

    Setting up npm and Node.js:

    Get Node.js here.

    • Visit https://nodejs.org/, the official Node.js website.
    • Get the most recent Long-Term Support (LTS) version that works with your operating system (Windows, macOS, or Linux) by downloading it.

    Set up Node.js:

    • After the download is finished, launch the installer and adhere to the wizard’s instructions for installation.
    • After selecting the installation directory and accepting the license agreement, the installation can begin.

    Check the Installation:

    • Launch a command prompt window or terminal.
    • Verify the installation of npm and Node.js by running the following commands:
    • The installed versions of npm and Node.js should be shown by these commands, respectively.

    NPM Package Overview for Lighthouse Audits:

    Lighthouse:

    • Google offers Lighthouse, an open-source tool for auditing SEO, accessibility, and other aspects of web page performance.
    • The npm command to install Lighthouse globally is as follows: Copy the programming and Installing Lighthouse with npm

    The puppeteer:

    • Google created the Node.js library puppeteer to control headless Chrome or Chromium browsers.
    • Lighthouse uses Puppeteer to generate reports and simulate user interactions.
    • Use npm to add Puppeteer as a dependency to your project: Copy the programming and Puppeteer install with npm

    Utilizing Node CLI to Conduct Lighthouse Audits:

    Using CLI for Lighthouse:

    • The following syntax can be used to run audits from the command line after installing Lighthouse globally: lighthouse <URL> –output-path <output_file_path.json> –output json
    • To save the audit report, replace <output_file_path.json> with the desired path and replace <URL> with the URL of the webpage you want to audit.

    Puppeteer Utilizing Lighthouse:

    • Lighthouse audits can be programmatically launched using Puppeteer by using its API to start a headless browser and then run Lighthouse audits.
    • For examples and best practices regarding the integration of Lighthouse with Puppeteer, refer to Puppeteer’s documentation.

    These steps will help you install the required npm packages for Lighthouse audits, set up a Node.js environment, and start efficiently analyzing web page performance and optimization opportunities.

    Lighthouse and Puppeteer Installation

    Using yarn package managers or npm package managers, installing Lighthouse and Puppeteer npm packages is simple. Here’s a detailed how-to:

    Making use of npm:

    • Install Lighthouse everywhere
    • Put Puppeteer in place locally

    Using yarn

    • Install the Lighthouse everywhere. 
    • Put Puppeteer in place locally:

    The Meaning of Puppeteer

    Google created Puppeteer, a robust Node.js library that offers a high-level API for programmatically controlling headless Chrome or Chromium browsers. Without a graphical user interface, it enables developers to carry out a variety of browser automation tasks, including creating screenshots, scraping websites, and simulating user interactions.

    Under the hood, Lighthouse uses Puppeteer to automate the loading of webpages, the gathering of performance metrics, and the creation of thorough audit reports. To mimic user behavior, Puppeteer starts a headless browser instance, navigates to the designated website, clicks links, fills out forms, and scrolls.

    Lighthouse can perform thorough audits of web pages thanks to Puppeteer’s capabilities, which include evaluations of best practices, SEO, accessibility, and performance. Lighthouse can reliably assess web page performance and spot optimization opportunities without the need for manual intervention by utilizing Puppeteer’s headless browsing capabilities.

    To sum up, Lighthouse uses Puppeteer as the underlying browser automation library to mimic user interactions, gather performance information, and produce informative reports. Through the installation of both Lighthouse and Puppeteer npm packages, developers can effectively utilize the combined power of these tools for web page performance analysis and optimization.

    Running Lighthouse Audits via Node CLI

    Using the lighthouse npm package, scripts can be written to automate the process of running Lighthouse audits via the Node CLI. This enables you to use command-line scripts to programmatically specify target URLs, audit configurations, and output formats. Here’s how to make this happen:

    1. Establishing the Project

    Be sure that npm and Node.js are installed on your computer before beginning to write the script. Run npm init -y in your terminal to start a new Node.js project and create a new directory for it. Next, use npm install lighthouse to add the lighthouse npm package as a dependency.

    2. Composing the Screenplay

    In your project directory, create a new JavaScript file (such as audit.js) and open it with your favorite code editor. The lighthouse package will be imported into this script, along with the configurations needed to run the audits.

    3. Running the Script:

    This will trigger Lighthouse audits for each URL specified in the script. The audit reports will be generated in the specified output formats (HTML, JSON, or CSV) and saved in the project directory.

    By writing Node.js scripts to automate Lighthouse audits, you can efficiently analyze the performance, accessibility, SEO, and best practices of your web pages and identify areas for optimization.

    Interpreting Lighthouse Audit Results

    It’s critical to interpret Lighthouse audit results to comprehend the performance of your website and pinpoint areas in need of development. Lighthouse offers comprehensive reports that include passed audits, opportunities for optimization, diagnostics, and a variety of performance metrics. Here’s how to properly interpret the results of a Lighthouse audit:

    1. Metrics of Performance:

    Lighthouse analyzes many performance indicators to determine how well your website performs overall. Among these metrics are:

    • First Contentful Paint (FCP): Calculates how long it takes to paint the first piece of content onto the screen.
    • Speed Index: The speed at which content loads visually is indicated by the speed index.
    • Largest Contentful Paint: The largest content element in the viewport’s render time is indicated by the Largest Contentful Paint (LCP) feature.
    • Time to Interactive (TTI): Calculates how long it takes for a webpage to respond to user input and become fully interactive.
    • Total Blocking Time (TBT): Measures the duration of the main thread’s blocking, which prevents it from responding to user input, during page load.
    • Cumulative Layout Shift (CLS): Quantifies unexpected layout shifts to determine how stable a page is visually.

    2. Possibilities for Enhancement:

    Lighthouse pinpoints particular areas where your website can be improved. These opportunities offer actionable insights for optimization and are grounded in industry standards and best practices. Typical opportunities include the following:

    • Reduce Render-Blocking Resources: To reduce render-blocking resources and speed up page loads, optimize the delivery of CSS and JavaScript.
    • Reduce Server Response Times: Use caching, optimize database queries, and send as few HTTP requests as possible to improve server response times.
    • Optimize Images: To minimize file sizes and enhance the speed at which pages load, compress and resize images.
    • Minimize Main Thread Work: To enhance page responsiveness, minimize main thread work, and optimize JavaScript execution.

    3. Diagnoses:

    Additionally, Lighthouse offers diagnostics to point out possible problems or trouble spots that could compromise the functionality of your website. These diagnostics provide information about particular problems that require attention, like:

    • Unused CSS: This tool finds CSS rules that are not in use and can be eliminated to speed up loading times and minimize file sizes.
    • Unused JavaScript: JavaScript code that is not being used is indicated by this flag, which can be safely removed to improve performance.
    • Accessibility Problems: Draws attention to problems with accessibility, such as inadequate color contrast or missing alt attributes on photos.
    • Security Vulnerabilities: Notifies you of possible security flaws like using out-of-date libraries or making unsafe HTTP connections.

    4. Successful Audits:

    Additionally, Lighthouse displays audits that your website has successfully passed. These audits highlight the sections of your website that already function well and adhere to recommended guidelines.

    Making Use of Lighthouse Ratings and Suggestions:

    Based on the aforementioned aggregated performance metrics, Lighthouse generates overall performance scores for your website. These scores assist you in evaluating the performance of your website in comparison to industry standards and pinpointing areas that need improvement.

    Prioritize your optimization efforts by concentrating on high-impact opportunities and diagnostics that could greatly enhance the functionality of your website. Start with optimizations that provide the biggest improvements in important metrics like visual stability, interactivity, and page load speed.

    Continually monitor the outcomes of Lighthouse audits and observe how performance scores evolve. Iterate continuously on optimizations and enhancements to guarantee that your website stays user-friendly, quick, and accessible.

    To summarize, the process of analyzing Lighthouse audit results entails comprehending performance metrics, spotting optimization prospects, attending to diagnostics, and setting priorities for work according to recommendations and scores. You can improve the functionality of your website and give users a better experience by making effective use of Lighthouse.