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 mods alike can be stored in these files. These are read second.

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 Game_structure.