The Item duplication glitch, also known as the Partyhat duplication glitch, was the most infamous glitch of RuneScape Classic, exploited on 7 November 2003. Its effects continue to have an impact on the economy of RuneScape today.
The glitch was not originally an attempt to duplicate items. A player named Sixfeetunder had been experimenting with RuneScape by using a third-party program called AutoRune in an attempt to simply trade the scythe. Although the player never managed to trade the scythe, he did discover how to create any non-stackable item. Therefore, the glitch did not duplicate existing items but instead created new ones.
The glitch was performed by trading with a player, and then using AutoRune to enter the numerical value that corresponded with a certain non-stackable item to have an item pop up and be traded to the other person. For example, the number for the Rune 2-handed sword was 81, so that value would be entered into AutoRune and the player who was trading with the one using AutoRune would be able to receive that item. The quantity of the item is shown as 0 on the trade screen of the player creating the item but it would show up as a quantity of 1 on the trade screen of the player receiving the item.
In his excitement, the experimenter revealed to very few people how to execute the glitch. These players then duplicated several items, the most expensive at the time: specifically partyhats, rune two-handed swords, and dragon square shields. The most expensive item, the purple partyhat, was created most amongst them. That day, though, one of these people revealed that the glitch existed.
before the incident
|Red||1,000,000 coins||See Runescape Wiki's entry|
|Yellow||2,500,000 coins||See Runescape Wiki's entry|
|White||4,000,000 coins||See Runescape Wiki's entry|
|Green||6,000,000 coins||See Runescape Wiki's entry|
|Blue||10,000,000 coins||See Runescape Wiki's entry|
|Purple||18,000,000 coins||See Runescape Wiki's entry|
Jagex permanently banned some players who were caught abusing the glitch. Jagex couldn't trace the partyhats/crackers, and so only a few accounts with billions of partyhats were banned. The only partyhats that were lost were the ones on the banned accounts, as no partyhats were deleted (this was confirmed in a Jagex News update the day of the event). As Jagex did not roll back the servers, the most expensive partyhat, the Purple partyhat, dropped to become the least expensive.
-  - Summary of the glitch from one of the players involved.