Java Edition:Long Sign
Signs from older versions could have more characters than currently possible.
Obtaining
15 Character Limit
From Infdev 20100607, when signs were fully implemented, until 14w21b (1.8 Snapshot), signs used a simple 15 character limit per line. In PC Gamer Demo, a sign spawns with line 1 and 3 having 16 characters but it does not save. In 14w25a, a new system was put into place that limited the number of characters per sign based on their width. By using 15 very long symbols in the same line before the new sign limit system, you can get a sign that would be impossible with the normal character size limits. The longest characters that can be put on a sign include "~", "_", and "m." Using the Languages method still allows signs with over 15 characters of long characters, so this is never discontinued.
Languages
By choosing the option "Force Unicode Font" in the language settings menu to ON, more characters can be typed into a sign than with the standard font due to this option reducing the visual size of characters.
Quotations
In 15w31a (1.9 Snapshot), every time signs are reloaded, they get quotations due to a bug.[1]
Resource Packs
In 1.13-pre6 and above, a resource pack can be used to set the width of characters smaller than usual. This allows for up to 65,522 characters per line before leading to errors during saving to NBT in singleplayer, or 384 characters per line in multiplayer due to packet size limitations. Going beyond this limit can lead to chunk regeneration.
One can find a premade resource pack to change the font size to 0.0001 here.
Gallery
A sign with 15 Ms on each line
The block data of a long sign with tildes viewed through commands to prove it is discontinued
