How to see what platform / cms other websites are using?

We want to help our clients succeed with their choice of platform, that's why we are presenting this method on how to find the platform that a website is using.

1. Builtwith – https://builtwith.com/ – Built With is a website that helps users discover what technology is used to build a website...
2. Whatcms – https://whatcms.org/ – Just enter the website url and the website will try to detect based on some rules what cms/platform the website is using.
3. Wappalyzer – https://www.wappalyzer.com/ – The best of all these I think is wappalyzer because it simply works...