From where to get the API key for the Programmable Search Engine that I have created? - Programmable Search Engine Community
Google Search for Discourse AI - Programmable Search Engine and Custom Search API - Integrations - Discourse Meta
TIL that Google allows you to create custom search for your website
Direct link to obtain a google custom search API key? - Stack Overflow
Videos
https://programmablesearchengine.google.com/
You can customize the layout, CSS, etc. Here is an example of search that I created for my website https://cse.google.com/cse?cx=210b5e0b95aee4c07&q=test#gsc.tab=0&gsc.q=Detecting%20and%20fixing%20flaky%20tests%20in%20Playwright
You can even upload your search result annotations and auto-completion suggestions. You can even use API to retrieve the results. It even provides statistics about the search usage. Overall, very impressed.
You can get an API key by visiting https://code.google.com/apis/console and clicking "API Access". You will then need to switch on the custom search API on the "Services" tab.
Wilfred's link got me started, but I didn't see the same thing as Wilfred. I had to click "Google APIs" (which links to here: https://console.developers.google.com/apis), then "Credentials".
"Custom Search API" is also available on the "Google APIs" screen if you need more information.