This page is dedicated to listing changes to NewGRFs which NewGRF authors should consider bumping the min_compatible_version to the current version of their newgrf as they have the potential to break the savegame and maybe even crash OpenTTD.

What is (in)compatibility

There are two kinds of compatibility:

• Changes which just add additional stuff to the NewGRF and don't influence any of exisiting things
• Changes which change the behaviour of existing things in a way that loading of a savegame works, but the game continues differently than with the previous version of the NewGRF. This is a grey area, but save to keep the compatibility maintained.
• Anything which results in a re-interpretation of the existing game state is incompatible. These are the important things to look out for

Incompatible changes

General for all features

• Changing or even removing the IDs of anything (changing (var)action2 IDs is safe)
• Changing the meaning of parameters (most often)

Vehicles

• Changing the length of vehicles
• Removing cargos from a vehicle

Stations

• Changing track / non-track state of tiles
• Changing track type of tiles

Industries

• Changing or removing an existing layout
• Changing or removing cargos

Houses

• Changing the size (in tiles) of houses