Duping?

Hi everyone,
Today I was searching trading forums etc. and I saw lots of headers including (NOT DUPED).
I know duping is serer sided and it is impossible but they include this for a reason I think.
Please if anyone know how to dupe something tell us !!!

yeah i have noticed this alot aswell people putting 'not duped' :/?

Yeah, sometimes one day I have 78 jarates, the next I have 79.

Pretty sure it's just random drops you're getting, but without displaying the "You found so & so." screen.

Duping is possible in any game that has items, it usually is complicated and 99.9% of times it's shared only with high ranked/respected persons in that games hacking. It's some kind of rule someone invented, and it's logic, cause if you share a dupe bug on a mmo with everyone, it will be patched in no time. Only elites know it and they will tell it only to other high trusted elites. I know it because there was, and still is on private servers, a dupe glitch on wow-wotlk. They patched it in cata because some genius went telling around. you know those "minor glitch fixes" they say, that's it. i'm going OT sorry, anyway there surely is a tf2 dupe glitch, but surely, it wont be shared.

Duping use to be possible but it is no longer capable of being done, there is likely another way but the old ways I knew how have long since been patched.

Duping was possible when the trading system was glitched.
For instead people could trade both in-game and through steam, enabling them to trade the item to 2 people at once.

Thanks for share, very useful.

I remember me and some friends would exploit that old trade system bug. I think that was the only dupe bug ever.