4BT File

What are 4BT files and how to open them

Are you having problems opening a 4BT 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 4BT files.

What is a 4BT file?

A .4BT file is a GoDot 4-bit Graphics Bitmap file.

GoDot 4-bit Graphics Bitmap is an image file format used by GoDot, a graphics editor for the Commodore 64, to store full-color 320×200 pixel artwork where each pixel has 4 bits of color depth (allowing 16 possible colors per pixel). It is used for creating, editing, and saving true multi-color graphics entirely within GoDot so that individual pixels can be manipulated in one of the 16 C64 colors. GoDot writes these .4bt files when a graphic is saved in its 4-bit "True Hires" mode.

The file is typically produced by GoDot's save/saver module called "4BitGoDot." When opened in GoDot, its full pixel data is restored; the format is compressed by GoDot when saved so that long runs of identical bytes are packed to save space. These .4bt files are used within GoDot workflows for painting, masking, color correction, and eventually exporting or converting to other Commodore-64 graphics formats or backdrops.

Each file begins with the ASCII signature GOD0 (bytes 0x47 0x4F 0x44 0x30) at offset 0. That signature identifies it as a standard GoDot 4Bit image. Immediately after comes the raw 4-bit per-pixel image data (with no stored address). Runs of three or more identical bytes are replaced by a flag byte ($AD), then a one-byte count (where zero means 256), then the repeated byte. The final byte of the file is also $AD, included as a GoDot signature but not interpreted as part of the image data.

How to open 4BT files

Important: Different programs may use files with the 4BT file extension for different purposes, so unless you are sure which format your 4BT file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 16, 2026

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