Brave, Firefox, and DuckDuckGo’s mobile browser not only have tracker blocking enabled by default, they will tell you which trackers they’ve blocked if you click the shield icon in the address bar. Using one of these browsers is probably the easiest way to see if the website you’re on is using trackers.
If you’re not using one of these browsers, you can also use a tool like Blacklight to see what trackers are being used by any given website. The EFF’s Cover Your Tracks tool is another interesting way to see how you may be tracked using browser fingerprinting.