GuestData

The GuestData cookie is a browser cookie that assigns a player's in-game name if they are a guest. It will always be negative. The last four digits are the common numbers guests have at the end of them, like "Guest 4182". These numbers are randomly generated every time the guest navigates the site, so it is possible to start off with 4182, click 'Discover' and then have 3486. These numbers used to be saved instead of being randomly generated on every navigation.
== Editing ==
People used to change their guest number by editing the cookie using tools such as EditThisCookie. Some YouTubers taught players how to change their guest number to sought out numbers, such as 0, 666, 1337, etc., in an effort to scare others. However, with the removal of guests in October 2017 and all methods of becoming a guest being removed in November 2018, it is no longer possible to play as a guest. Roblox has never announced a return for guests, and due to how long ago they were removed, they will likely never reappear.
== Alternative Method ==
There were a few lines of code that were rarely known about. They could be found from the Roblox website when you select your gender through Guest Mode. You can find this code by Inspect Element. The code was only visible when you enter a game through Guest Mode.
roblox-player:1+launchmode:play+gameinfo:Guest:-(GUESTID)+launchtime:1519425624744+placelauncherurl:https://assetgame.roblox.com/game/PlaceLauncher.ashx?request=RequestGame&browserTrackerId=14353303313&placeId=(PLACEID)&isPartyLeader=false&genderId=1+browsertrackerid:14353303313
(GUESTID) = Negative ID of Guest. Leaving the (GUESTID) blank will result in random selection from all Guest IDs from -1 to -2147483647. That number specifically being the eighth Mersenne prime. Some of these from -1 to -9999 give you the same positive number in the name, while others give different numbers.
(PLACEID) = Place you want to join
(GENDERID) = The Gender of your Guest
* 1 = Cap Guest (Gender Neutral)
* 2 = Male Guest (Blue Hair)
* 3 = Female Guest (Pink Hair)
* nothing = Cap Guest (Gender Neutral)
When you enter your code into the address bar and press enter, it would load you into the place with the genderid and guestid of your choice.
== Trivia ==
* Before the Guest Removal of 2018, adding an infinity sign into the GuestID would result in always joining the game as Guest 8. The reason for this is unknown.