Share custom tracks through established community channels and describe the game edition, environment and validation status clearly. Legacy Trackmania maps commonly use the .Challenge.Gbx extension, but compatibility can depend on the game edition and the map itself.
Check the edition
Do not assume that every file from another Trackmania generation will work in Nations Forever or United Forever. Nations focuses on Stadium, while United includes additional environments.
Download safely
Use the Njoy forum for discussion and the downloads page for resources Njoy has actually reviewed. Scan unexpected archives and avoid executable files.