The purple partyhat is an item that was originally obtained by opening a Christmas cracker during the 2001 Christmas event. Partyhats are some of the oldest discontinued items in the game, beaten only by the pumpkin. This has resulted in them becoming some of the most expensive items in RuneScape's history, far exceeding the maximum cash value and resulting in them being traded almost exclusively outside the Grand Exchange. Following the update to Grand Exchange and the money pouch, partyhats are once again traded through the Grand Exchange.
Before free trade, the street price was much higher than the GE price, giving the false impression that partyhats sharply rose when free trade was reintroduced. Purple partyhat maintained the cheapest partyhat until mid 2019; by the end of 2019 it had overtaken both yellow and green partyhats in price becoming the 4th most valuable partyhat.
During the 15 Days of Christmas in 2013, this item, along with other Christmas-themed equipment, were given the Hybrid style of combat, and stats that scaled with the player's levels. This was so players could use these items in combat to assist in hunting for festive crackers during the event.
In RuneScape Classic, partyhats were simply called "party hat" with no colour in their name. What is now the purple partyhat was more magenta in colour, but players called it pink. After the release of RuneScape 2, Jagex made a slight colour change to the "magenta" partyhat, and then named it purple partyhat.
The purple partyhat was originally the most expensive of the partyhats, but became the cheapest after the Partyhat duplication glitch.
Since there was no rollback of the servers after this glitch had been fixed, players who own a purple partyhat will never know if they have a real or duplicated partyhat.