To audit core web vitals Of Any Website, check the following steps-

To create a free PageSpeed Insights API key, login to Google account and then visit the google developer’s PageSpeed Insights page.

Then, scroll down and click on the ‘Get a Key’ button.

After Clicking “Get a key” button, then enter the project name, agreeing to the terms and conditions and clicking ‘next’.

After clicking the next button, the API key will be generated

The key- AIzaSyCUc4YuFC6v4zEocYREMDraP8pEqeUs848

Click on ‘Done’.

Go to ‘Configuration > API Access > PageSpeed Insights’, on the Screaming frog spider, enter the previously created PageSpeed Insights API key:

Then click on “Connect” button

After connecting the API key, go to the Metrics tab. Select either mobile or desktop data. Then select the data from PageSpeed Insights which are reported for each URL.

Crawl the website after selecting the metrics data.

Click on the PageSpeed Tab to see all URLs which have speed data reported from the API:

The PSI Error and PSI Status columns are indicating if the API failed to fetch any data for particular URLs.

From the PageSpeed tab, if scroll to the right, there are the CrUX metrics collected from the API:

The first column is the ‘Core Web Vitals Assessment’. This will be marked as either a Pass or a Fail depending on whether It is considered Good in all three Web Vitals.

Here different filter opportunities are present. Choose the filters one by one to check the issues.

Export the URLs, and reduce the unused javascript code for these URLs.

Check all the filters one by one. If issues are found, then export the URLs and fix that particular issue, else no need to take action.

Source: How To Audit Core Web Vitals - Thatware