Hi @ferero18 ,
Can you share your store URL so that we can do a comprehensive study on the issues, and let you know the steps on how the web vitals and speed scores of your website can be improved?
For your information, Core Web Vitals along with website speed scores play a significant role in improving the website’s overall ranking on google.
On GtMetrix & Page speed insights, you witnessed such contrasting scores because GtMetrix measures the performance of the website on the desktop.
Whereas the lighthouse or page speed insights primarily measure performance on mobile devices whose scores are generally lesser compared to desktop scores.
Web vitals majorly comprises four parameters such as LCP, FCP, CLS & TBT along with other parameters. And so LCP plays a crucial role in measuring web vitals.
To improve your LCP score, you need to ensure that the most important scripts and CSS files, which are responsible for the layout of the website load first, then other resource files can load afterward.
In order to work on the CSS files you should preload them and then use them on your website code. And to work on the JS files, you can use async and defer attributes.
Hope it helps. Let us know if you need any other help.
Thanks & Regards
CedCommerce