null is a reserved constant used in Java and similar programming languages to represent a void reference. In simpler terms, it is a value used to represent that a reference variable has no set value. In RuneScape it usually appears in string values either due to a variable not being assigned in time, usually due to lag, or as a result of a glitch.
It first made its appearance in game as a player name some people would see from time to time in RuneScape Classic. It was a rare occurrence, and is usually a glitch to be fixed by Jagex. This can occasionally appear when moving between areas like going up and down stairs. One strange part about the sighting was that the "n" at the beginning of the name was lower case, where names in RuneScape were always capitalised automatically, before Display names were released. This usually occurred when players with dial-up, or similar low speed, internet logged in and tried to type something.
Null was featured on the God Letter 6: "Null is a mystical guardian who protects you when you enter new areas. He is a passive and benevolent force, and as such his combat level never rises above 1." - Saradomin
An item also can be called "null". It means the same at the top of the page, the information of the object didn't load. Strangely the "null" object's name never changed. Previously, if one typed in 'null' on the quick chat system, this item could be said. This was removed in a hidden update.
If you search bank item "null" you get a message stating a number of search results equal to the number of empty spaces in your bank, possibly meaning that there could be an item "null" that represents empty bank space.
Sometimes when playing soul wars, null might appear when you fail to use a bandage on someone.
|Null's inventory icon|
Null appears for a split second almost 50 percent of the time when smelting ores in Daemonheim. By using an item that disappears upon use, such as using cider on locals for the Seer's Tasks, and by quickly right clicking and selecting 'use item' before the item disappears, once the item disappears, the top left part of the screen shows 'null->' and if you hold your mouse over an item, it shows 'null->item' as if 'Null' is an item being used.
Sometimes, when making items, "null" is displayed for a split second in the "How many would you like to make?" interface. This tends to happen more often while smelting. Also, null can be made by dropping an object, then right clicking the object again before it is removed from your inventory, click "Use" and right click on another object.
Sometimes, immediately after logging in, if a player talks, or the game makes the player say something, the player's name will appear as 'null' in the chat box.
In Legacy of Seergaze, players repair a furnace. For a time after the quest was released, players could stand on the story above, and see the furnace through a hole in the floor. They could right-click on the top of the furnace (which registered as non-interactive scenery), and the menu would include the option "Examine null". This was later fixed by Jagex.
Adventurer's log Null
When Livid Farm was released, the Adventurer's log became glitched resulting in all of the entries reading "null". Examples include:"Item Found : Null.", "I killed null null", "I killed null null null null null null in Daemonheim." or other similar sentences. This happened for everyone with sentences containing a boss monster name, item names, or a completed treasure trail. For quest completions, it displays the title correctly, but then just says 'null'. This was finally fixed on 12 April 2011.