The single fastest filter for whether a CS2 trading site is real is to watch the URL bar when you click the Steam login button. Real sites use Steam's official OpenID, which redirects you to steamcommunity dot com, meaning you're typing your password on Steam's servers, not the trading site's. If the URL bar doesn't show steamcommunity when you're entering your credentials, close the tab.
Most people skip this because the fake login pages are visually identical to the real ones, and the domain is the only reliable tell at that point.
Beyond the login flow, domain age is the fastest additional filter. Real marketplaces have years of registration history, while clone sites are almost always under 6 months old, and a Whois lookup takes 10 seconds. For Reddit verification, search the exact site name. Real marketplaces have complaint threads about specific disputes, while sites that ran off with inventories have a different pattern of complaints entirely, and the distinction is more useful than the volume.
The main attack vector right now is Discord DMs. Fake "verified traders" send links to clone sites with one-letter domain differences, and both the page and the login form look real, so the URL bar is the only check that catches it consistently. If you found a site from a search engine and it has Reddit discussion history, you're very likely fine. If someone on Discord or Steam introduced you to it, treat it as hostile until you've independently verified the domain.
Stay safe out there.
Source: r/DefaultAlive · by /u/derekiveyy679