From Spring

Spring supports reading from zlib zip and non-solid 7zip files. The filenames for these compression types must be .SDZ for zlib and .SD7 for 7zip respectively. They are standard files, just with different extensions for Spring. Here's a list of all filetypes supported by Spring; a higher read order means the contents of a file of that extension will take priority over files of a lower read order.

Read Order File Extension Compression Method Description
1 SD7 Non-Solid 7zip A 7zip file with the extension changed to .SD7. 7zip compressed archives generally have the highest compression (and therefore lowest filesizes). Files of this type are read first.
2 SDZ ZLIB ZIP A zlib ZIP file with the extension changed to .SDZ. Maps and games alike can be stored in these files. These are read second.
3 SDD uncompressed A normal folder with the extension .sdd added. Used only during development because it is possible to test the game/map without having to unzip/zip it for every change.

The best tools to use to view the contents of a compressed Spring file, and to pack and unpack the contents of such a file are:

  • WinRAR to view, browse, extract, and pack SDZ files, or to browse SD7 files.
  • 7zip to view, browse, extract, and pack SD7 files.

For the internal file structure of a Spring package, see Gamedev:Structure.