React - Lighthouse Performance audits

Very important for this part is the font load time. For faster load, it can be used the font-display: swap. This will make the site to render the default font and when the loading is done, the font will be changed. Also, you can preload the fonts. 

It measures how long it takes a page to become fully interactive. A page is considered fully interactive when:

• The page displays useful content, which is measured by the  
• Event handlers are registered for most visible page elements, and
• The page responds to user interactions within 50 milliseconds.

To improve this metric, you should consider 

Also, other things that can be helpful: 

and 

PRPL is an acronym that describes a pattern used to make web pages load and become interactive, faster:

• Push (or preload) the most important resources.
• Render the initial route as soon as possible.
• Pre-cache remaining assets.
• Lazy load other routes and non-critical assets.

While anything you do to improve page load speed will improve your Speed Index score, addressing the following should have a particularly big impact:

TBT measures the total amount of time that a page is blocked from responding to user input, such as mouse clicks, screen taps, or keyboard presses. The sum is calculated by adding the blocking portion of all 

Try to diagnose the root cause of long tasks, using 

In general, the most common causes are:

• Unnecessary JavaScript loading, parsing or execution. This means the main thread is doing more work than it supose to do -> try reducing JS payloads with code splitting, removing unused code and efficiently loading third-party JavaScript
• Inefficient JS statements -> avoid selectors that returns 2000 nodes (e.g. document.querySelectorAll('a') ) and refactor to have a more specific one.

This approximates when the main content of the page is visible to the users. 

The elements that are taken into consideration for Largest Contentful Paint: 

• <img> elements
• <image> elements inside an <svg> element
• <video> elements (the poster image is used)
• An element with a background image loaded via the   

In the future, additional elements might be added, like <svg> and <video>

Extra info: 

Causes: 

• Slow server response times
• Render-blocking JavaScript and CSS
• Resource load times
• Client-side rendering

For improvements, some relevant techniques:

CLS is a measure of the largest burst of layout shift scores for every 

How to improve:

• Always include size attributes on your images and video elements, or otherwise reserve the required space with something like

• Never insert content above existing content, except in response to a user interaction. This ensures any layout shifts that occur are expected.

• Prefer transform animations to animations of properties that trigger layout changes. Animate transitions in a way that provides context and continuity from state to state.

More info: