| Extension | Definition | Published files | Description |
| .CMP | cds.pdf, chapter 2.9, format v331 | v331 (GTA1/London69/London61) | Compressed Map file, referenced by mission.ini |
| .ROP | cds.pdf, chapter 2.6 | No | Police Route File. Only for development |
| .PRB | cds.pdf, chapter 2.6.1 | No | Road Block File. Only for development |
| .GRX | cds.pdf, chapter 3.6, format v290 | No | For editors only |
| .GRY | cds.pdf,
chapter 3.6, format v325 (but chapter 3.7 writes v305) |
v325 (GTA1/London69/London61) | 8-bit graphics, Referenced by .cmp |
| .G24 | cds.pdf, chapter 3.8.1, format v336 | v336 (GTA1/London69/London61) | 24-bit graphics, Referenced by .cmp |
| .SAM | No definition found | No | Speech samples for area names, referenced by .cmp;
however, all .cmp files reference 0, i.e. not using SAM. The spoken area names are instead in the SDT files with index 100+sample_id The 100 seems to be hardcoded, as it is not the 100 we see in the mission.ini header |
| .MAP | No definition found | v331 (London1969/London61) | Uncompressed map file. Only for development. A leftover can be found in GTA London. |