Performance is a visceral part of the user experience. For many websites, an improvement to the user experience by speeding up the page load time aligns with an improvement to conversion rates. Conversely, when performance is poor, users don't convert as often and have even been observed to be rage clicking on the page in frustration.

Website optimization tools are essential to improving your site's performance.

Lighthouse

Lighthouse is a page experience tool built by Google and was initially meant to audit Progressive Web Apps (PWA). The tool executes five audits for accessibility, performance, SEO, Progressive Web Apps and an extended list of best practices. Powered by the new Core Web Vitals, these audits together give you an excellent overview of the quality and performance of your mobile website as well as your desktop site, or web app. Lighthouse plugins which are a way to extend the feature of Lighthouse with insight from domain experts (that's you!) and share this extra feature with other Lighthouse users.

Run Lighthouse on browser

Open dev tools and run Lighthouse under Lighthouse tab.

Run Lighthouse Via Cmd

Install Lighthouse package

npm i lighthouse
npm install -g lighthouse

Run on web:

https://web.dev/measure
Global performance insights for your site | Lighthouse Metrics
Enter the URL of your site and click the "Run Test" button. Then you will be redirected to your report page. All tests…lighthouse-metrics.com

Yellow Lab Tools(https://yellowlab.tools)

Yellow Lab Tools is an open source project by Gaël Métais. It allows you to test a webpage (via an URL) and detects performance and front-end code quality issues.This is done by loading the webpage via PhantomJS and collecting various metrics and statistics with the help of Phantomas. These metrics are categorized and transformed into scores. It also gives in-depth details so that developers can correct the detected issues.Which shows JS-Timeline and JS profile.

Fast or Slow(https://www.fastorslow.com/)

Fast or Slow is a global performance monitoring solution for your websites that detects and reports on the most important factors in your users' experience of your website. Fast or Slow measures this experience from a variety of locations, giving you a wide overview of how site visitors experience your site.
Fast or Slow measures a number of different parameters that help you understand your website's performance from various locations around the world. These parameters include:
First Contentful Paint
First Meaningful Paint
Time to Interactive
Total Blocking Time
First CPU Idle
Speed Index
Round-trip Time
Transfer Size

In addition, Fast or Slow performs audits on your website content to determine where speed improvements can easily be made, and keeps a history of past audits for each site. Fast or Slow is based on Lighthouse, an open-source, automated tool for testing web pages.

WebPageTest(https://www.webpagetest.org)

WPT measures how a particular web page loads. As the page loads, a number of useful metrics are captured, cataloged and then displayed in various charts and tables useful for spotting performance delays. These metrics and visuals can help us answer the important questions we listed above. You can also control many aspects of WPT's analysis such as the platform to use (desktop vs mobile), browser of interest (Chrome, Firefox, IE, etc), and even the geographic location.