Overview of web performance

Web performance is measured by key metrics called Core Web Vitals. These metrics quantify your online store's performance, and optimizing the values can improve the shopping experience of your customers, your conversion rate, and your store's discoverability.

Your online store's performance can be influenced by several factors, such as the following areas:

Apps
Third-party libraries and services
Analytic libraries
Theme code
The quantity and size of images and videos

By making strategic adjustments to your online store, you can improve your performance metrics and ranking.

Measuring your web performance

Web performance is measured by Core Web Vitals, which include the following performance measurements:

Largest Contentful Paint (LCP) measures loading speed, based on how fast the largest element or main content becomes visible to visitors. A good LCP score is achieved when the main content is loaded within 2.5 seconds from the start of the page load.
Interaction to Next Paint (INP) measures interactivity based on how long it takes the page to become responsive to most user actions, such as clicking a link or a button. An INP score of less than 200 milliseconds is considered a good performance as the page becomes interactive quickly.
Cumulative Layout Shift (CLS) measures visual stability, based on how much the content shifts around unexpectedly when navigating around the page. A CLS score of less than 0.1 is considered a good performance.

For your web performance to be considered "good" by search engines such as Google, at least 75% of your page loads need to achieve Good scores across all Core Web Vitals. The web performance reports show this 75th percentile measurement to help you track your performance.

In addition to the Core Web Vitals, Google evaluates other factors, including the following examples:

Mobile compatibility
Safe browsing
HTTPS security
The absence of intrusive interstitials, which are page elements that obstruct a complete view of the content, such as promotional pop-ups or age verification

These factors together help evaluate a webpage's performance and user experience.

Learn more about Core Web Vitals and Google search results.

How web performance impacts your store

Your online store’s performance can impact the shopping experience of your customers, your conversion rate, and your store's discoverability.

Learn more about why web performance matters.

Experience and conversion

When your online store loads quickly and interactions are smooth, it provides a positive experience to all visitors regardless of their device or connection speed. If a site is slow or difficult to navigate, then visitors are more likely to leave before they buy something. By improving your store's web performance, you can enhance user experience and increase conversion rates.

Discoverability

Search engines such as Google use page speed as a ranking factor. If your online store pages perform poorly across the Core Web Vitals, then they might be ranked lower, even if your store is otherwise optimized for search engines. By improving web performance, you're improving your store's chances of being ranked higher in search and getting more visibility for your business.

Online store features vs. web performance

Your online store is made up of a set of features, such as theme code, apps, images, videos, carousels, social media feeds, and analytics. These features can enhance the visitor experience and extend your site's capabilities.

However, each feature that you add to your online store can impact your store's Core Web Vitals. Some features can slow down your site or create unexpected behaviors that can impact user experiences.

When you consider adding a feature to your store, you should weigh the benefits of the feature against its impact to the Core Web Vitals. You might need to find the balance between user experience and web performance.

Ask yourself the following questions when considering features for your store:

What will help customers make the decision to purchase from the store?
- For example, consider whether your customers would prefer a simple homepage with links to detailed product pages, or a more powerful home page where they can quickly view and buy products.
What functionality should exist at the top of the page to drive conversion?
- For example, branding elements, featured images, and a checkout cart are all features that can impact performance but increase conversion.
What functionality can load later as customers scroll down the page?
- For example, analytics and product reviews don't need to be loaded immediately when a customer visits your store. You might need to consult your theme or app developers to understand if a feature is loading right away.

Explore your web performance metric summary and reports

You can learn how your store performs across the Core Web Vitals by viewing your web performance reports. The reports and performance metric summary display how your store ranks across all 3 Core Web Vitals and provides actionable insights for improving.

You can also explore factors that impact your web performance and how to address them.

Frequently asked questions about web performance scores

Why don't I have scores yet?

The following are some reasons why you might not have a score for your core web vitals yet:

Your store is password-protected: If your online store is password-protected, then you won’t have the real-user traffic necessary to generate Core Web Vitals. You need to remove the password page to allow users to visit your site.
You don’t have traffic yet: You might not have had any page views to your online store to generate real-user metrics. If you haven't had any traffic, then you can use a free performance analysis using synthetic data, such as PageSpeed Insights.

Why do I have traffic but no Core Web Vital scores?

Core Web Vitals are a Google product and currently only available on Firefox and Chromium-based browsers. Modern browsers are built upon similar technologies and so the existing data still represents an accurate depiction of how your users experience the website.

Both Largest Contentful Paint and Interaction To Next Paint are anticipated to become available in one of the upcoming Safari versions. Learn more about cross-browser interoperability in the Interop 2025 project.

Why do I have scores for some metrics but not others?

Each metric measures a different aspect of performance and user interactions. For example, Largest Contentful Paint measures page load, whereas Interaction to Next Paint measures interactions with buttons or links. If there are no interactions with the elements on the page, then the INP metric might not have a score.

Why did one of my scores change?

Scores can fluctuate due to traffic amount or changes made to your online store. If there are big fluctuations due to low traffic, then try changing to a weekly or monthly filter.

Your scores can also change when you make changes to your online store. For example, you might have imported several new products, created several new collections, changed your theme, or introduced a new app. Learn about the factors that can impact your online store performance.

Why are the scores on my web performance reports different from other tools?

The scores in your web performance reports might differ from other tools due to the following factors:

The data in the web performance reports is based on the UTC standard, which might differ from other platforms' timezones.
The web performance reports collect data differently by gathering a broader data set from all Chromium browsers (Chrome, Opera, Edge, Samsung Internet) and Firefox. Tools such as Google’s PageSpeed Insights use the CrUX report for opted-in Chrome browsers only. Learn more about CrUX data.