Real IP vs. Proxy — How do platforms tell the difference?

How do platforms distinguish between a residential (physical) IP and a proxy/residential-type proxy IP? Are there any reputable tools or websites that can reliably tell whether an IP is a proxy or a real residential IP?

I’m investigating how platforms identify whether an IP is a true residential/mobile (physical) IP or a proxy (including residential-type proxies). What indicators and data sources are typically used for this classification? Also, are there established services or tools you recommend for checking an IP’s proxy/residential status?