SEOPress PRO 5.3 is required.
The first step is to sign in to Google Cloud Console.
Note that you must first create a Google Console project before you can follow this tutorial. More info on the official documentation.
Then, select your projet from the top bar and open the main menu (by clicking the hamburger icon).
Go to APIs & services, Library page.
Search for: PageSpeed Insights API.
Click on the first result and Activate the API.
Once done, click on Manage button.
From the left menu, click on Credentials tab, then on “To view all credentials visit Credentials in APIs & Services“.
Click on Create credentials button and select API key.
Copy and paste the generated API key to your WordPress admin, SEO, PRO, Page Speed Insights tab, “Enter your own Google Page Speed API key” field.
We suggest you to restrict your API key to your own domain name from Google Cloud Console for security.