CTY File

What are CTY files and how to open them

Are you having problems opening a CTY file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CTY files.

What is a CTY file?

A .CTY file is a SimCity City file.

SimCity City files hold a complete saved city from early versions of SimCity developed by Maxis. These files store everything required to resume building a virtual city: terrain layout; roads, buildings, zones, and decorative objects such as trees; simulation settings like starting money; and various global city state variables. The default layout (including terrain and basic settings) used when starting a new city uses a template named "default.cty."

Maxis' SimCity program is what produces these files when a city is created or saved. SimCity - and in some cases SimCity Classic or SimCity 2000 - reads them back in to resume the simulation or present the city exactly as it was saved. These files date back to the original 1989 DOS version (Micropolis) and early PC/Mac ports.

Each SimCity City file begins with a small header section (often around 128 bytes in size) followed by a full map grid area storing the city's terrain and structures. The grid is typically 120 tiles wide and 100 tiles tall. Tile data values are stored as 16-bit big-endian words.

As identifiers, the file starts with a zero byte at offset 0, and at offset 65 appears the ASCII signature "CITYMCRP." These serve to distinguish genuine SimCity City files from other files.

How to open CTY files

Important: Different programs may use files with the CTY file extension for different purposes, so unless you are sure which format your CTY file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested two different CTY openers which you will find listed below.

Last updated: September 19, 2026

Various apps that use files with this extension

These apps are known to open certain types of CTY files. Remember, different programs may use CTY files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CTY file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.