The PageSpeed API is used for both the PageSpeed requests (Desktop & Mobile) AND also for the mobile-friendly request.
To access Google’s PageSpeed API you’ll need to authorise URL Profiler by creating a Public Access API Key. You can get a free Google PageSpeed API key from within Google’s Developer Console.
Note: If you already have an API key set up for Google Safe Browsing, you can use the same API key for PageSpeed. You just need to enable the API (Step 2 below) and then use your existing API key for both PageSpeed and Safe Browsing (Step 5).
UPDATE: For Mobile Friendly to work properly, please enable Google Search Console API.
1. Create Project
First you need to create a project. Hit the 'Credentials' option in the left hand navigation, then on the Create Project screen, name your project 'URL Profiler' and click to create it.
2. Enable API
Now, navigate to the 'Library' screen from the left hand navigation.
Before you create the key, you’ll need to make sure you have authorised the PageSpeed Insights API. Search for 'pagespeed' in the search box.
That's the one we want, so just click into it.
Then just hit the blue button 'Enable'.
3. Create API Key
Now, you need to create the key. Head over to the “Credentials” section, and you'll be faced with a 'Create credentials' overlay.
Click the blue dropdown, and choose the first option 'API key.'
4. Copy API Key
This will create your API key, which will display in the overlay box.
Copy the API key, and close the window down.
5. Paste into URL Profiler
Paste the key into the Google PageSpeed box on your URL Profiler Account Settings.
You're all set! You can now get Google PageSpeed Insights data back for any list of URLs (by default limited to 25,000 requests a day), and/or perform mobile-friendly checks on a list of URLs.
Simply tick any combination of the buttons: Mobile Friendly, Mobile PageSpeed, Desktop PageSpeed - all of which are powered by the PageSpeed API.