- This article is about the file format; for the file extension, see .erf.
ERF is an acronym for encapsulated resource file, a BioWare file type containing multiple game resources. This is a container file format, similar to RAR, TAR, or ZIP, without compression. Neverwinter Nights files that use the ERF format include imports/exports to/from the Toolset (.erf), hak paks (.hak), modules (.mod), and BioWare modules (.nwm).