There are many reasons why you might want to know what technologies a site is running. You might like how the site looks or functions, and want to copy it. Or you might be a security tester looking for vulnerabilities.
For a long time, BuiltWith was pretty much the only option out there, but it’s a paid offering once you hit a certain amount of usage.
Wappalyzer (Web App Analyzer) is a great alternative.
Wappalyzer is not only great for doing scans right on the website itself, but they also make a bookmarklet available. Drag that link to your favorites bar and click it on any site you’re on and it’ll give you a display like the one above.
Finally, and perhaps best of all—you can download the entire tool for free and run it yourself. So instead of having to spam the website itself with requests, you can have your own copy running locally that you can hit as much as you want.
So if you make a lot of requests, have issues with paying for API access to BuiltWith, or are getting throttled making web requests to one of the tools, I highly suggest checking out Wappalyzer.