An FEA file is a data file commonly used in .UFO files to store font data. It contains Adobe Font Development Kit for OpenType (AFDKO) feature definitions, which may include language coverage, ligature, kerning, contour, and cursive information. FEA files are saved in plain text.
FEA files are typically found in UFO files, along with .PLIST, .GLIF, and .PNG files. The files should not be removed from UFO files and are commonly accessed when a program, such as FontForge, RoboFont, or Glyphs, opens the UFO file. However, if you need to manually view an FEA file, you can open it in a text editor since it is saved in plain text.