determine whether items are counterfeits based on an AppID whitelist
Download any user script manager, like Tampermonkey, Greasemonkey, or Violentmonkey. Then click here to install the userscript. It should update automatically.
Items that may be counterfeits will show up like the following in trade offer windows (the item image, if any, will appear in front of the stripes)
The apps that will not trigger this warning are:
440, // Team Fortress 2
570, // Dota 2
620, // Portal 2
730, // Counter-Strike: Global Offensive
753, // Steam
4920, // Natural Selection 2
207140, // SpeedRunners
227300, // Euro Truck Simulator 2
232090, // Killing Floor 2
234010, // Warframe
238460, // BattleBlock Theater
238960, // Path of Exile
244850, // Space Engineers
244930, // SNOW
250820, // SteamVR
252490, // Rust
264710, // Subnautica
270450, // Robot Roller-Derby Disco Dodgeball
270880, // American Truck Simulator
290340, // Armello
295110, // Just Survive (H1Z1)
322330, // Don't Starve Together
323850, // Move or Die
338170, // Ratz Instagib 2.0
394690, // Tower Unite
417860, // Emily is Away
431240, // Golf With Your Friends
431960, // Wallpaper Engine
433850, // H1Z1
437220, // The Culling
464350, // Screeps
471550, // Nine Parchments
517710, // Redout: Enhanced Edition
578080, // PLAYERUNKNOWN'S BATTLEGROUNDS
684850 // Shoppe Keep 2
This list is incomplete. App developers or other interested parties looking to add apps to the whitelist may send a request through GitHub issues. I and others will weigh an app's legitimacy and risk and, if appropriate, add the app to the whitelist.
GNU GPL v3. See LICENSE