Data File
File Extension: .esm .esp
Master Files(.esm) and Plugin Files(.esp) are the core data files of Fallout. By tradition, the file extensions stand for Elder Scrolls Master and Elder Scrolls Plugin. A master file acts as a database of all of the data for the world, including object data, dialogue, gameplay settings, object placements, AI settings, landscape, cells, etc. The Creation Kit is the tool we use to view and edit master files and plugins.
Master files and plugins are largely identical in format, but have some important distinctions in practice. A master file is autonomous; it relies on no information other than itself. The Creation Kit will not create master files. A plug-in (ESP) file relies on information from a Master ESM file. Plug-ins can only refer to information in another plug-in indirectly by using scripts. They can only refer directly to data from a master file (though they can refer to multiple master files).
Tooling
- The Creation Kit is the primary tooling for working with data files.
- There are community software projects that provided tooling for working with data files.