Optimize images for Core Web Vitals
Lean how images affect the Core Web Vitals en how to optimize them
How Images Can affect the Core Web Vitals?
Images play a significant role in enhancing the visual appeal of a website, but they can also have a significant impact on its loading speed. Core Web Vitals are a set of metrics that Google uses to measure the user experience of a website, and image optimization is a critical factor in achieving good scores. In this article, we will discuss how to optimize images for Core Web Vitals and improve your website's loading speed.
Understanding Core Web Vitals
Before we delve into image optimization, let's briefly review the Core Web Vitals. They are a set of user-centric metrics that measure the loading speed, interactivity, and visual stability of a web page. The three key metrics are:
Largest Contentful Paint (LCP): measures the loading speed of the largest element on the page.
First Input Delay (FID): measures the time it takes for the page to become interactive.
Cumulative Layout Shift (CLS): measures the visual stability of the page.
Google considers a website to have good user experience if it meets the following benchmarks:
LCP: under 2.5 seconds
FID: under 100 milliseconds
CLS: under 0.1
How Images Can affect the Core Web Vitals?
Images can affect all of the Core Web Vitals.
Largest Contentful Paint
One of the Core Web Vitals is Largest Contentful Paint (LCP), which measures how long it takes for the largest element on the page (such as an image or video) to become visible to the user. If an image is too large or takes too long to load, it can significantly slow down the page's LCP score.
Cumulative Layout Shift
Another Core Web Vital is Cumulative Layout Shift (CLS), which measures how much the content on a page shifts around as it loads. Images can cause layout shifts if they are not properly sized or if they are inserted into the page after it has already loaded, causing other elements to move around.
First Input Delay and INP
Finally, images can also impact the third Core Web Vital, First Input Delay (FID), which measures the time it takes for a user to interact with a page. If there are too many large images or if they are not properly optimized, the page may take longer to respond to user interactions, leading to a poor FID score.
How to optimize HTML images element for speed
Specifies the URL of the image. This property is essential, as it tells the browser where to find the image.
Width and height
Specifies the width and height of the image in pixels. These properties are important for rendering the image correctly on the page, as they define the size of the image container and how the image fits inside it.
Specifies alternative text for the image if it cannot be displayed. This is important for accessibility purposes, as it helps visually impaired users understand what the image is about. It's also important for search engine optimization (SEO), as search engines use the alt text to understand the content of the image.
Specifies how the browser should load the image (lazy, eager, or auto). This property is important for improving page performance, as it allows images to be loaded asynchronously and only when they are needed.
The fetchpriority attribute specifies the priority of a resource's fetch relative to other resources on the page. The priority attribute can have one of three values: "high", "medium", or "low". A resource with a high priority is loaded before resources with medium or low priorities. A resource with a medium priority is loaded before resources with a low priority. Resources with the same priority are loaded in the order that they appear in the HTML. >
New and faster image containers
Images are often one of the largest resources on a webpage, and they can significantly slow down the loading speed of a page if they are not optimized. Newer and faster image containers, such as the WebP and AVIF formats, can help reduce the file size of images without sacrificing their quality. This means that they can be loaded more quickly, which can improve the loading speed of the page.
Image strategies for the LCP element
Image strategy for logo's and other visible non LCP elements
Image strategy for below-the-fold images
I help teams pass the Core Web Vitals:
A slow website is likely to miss out on conversions and revenue. Nearly half of internet searchers don't wait three seconds for a page to load before going to another site. Ask yourself: "Is my site fast enough to convert visitors into customers?"