IFEFFIT is an interactive program and scriptable library for XAFS analysis, combining the core algorithms of AUTOBK and IFEFFIT with data manipulation and interactive graphics. It offers a command-line interface for interactive or batch processing and a library of functions accessible from C, Fortran, Tcl, Perl, and Python. IFEFFIT supports XAFS analysis procedures, Fourier transforms, and FEFF calculations, as well as data plotting and algebraic manipulation. The library is designed to be flexible and programmable, allowing users to create and save macros for repetitive tasks. IFEFFIT uses the PGPLOT graphics library for plotting and can be built without built-in graphics. It is available under an Open Source license and is still in development, with plans to add advanced features like simultaneous fitting of multiple datasets and improved background refinement. G.I.FEFFIT, a graphical user interface for IFEFFIT, provides a user-friendly environment for data analysis and plotting.IFEFFIT is an interactive program and scriptable library for XAFS analysis, combining the core algorithms of AUTOBK and IFEFFIT with data manipulation and interactive graphics. It offers a command-line interface for interactive or batch processing and a library of functions accessible from C, Fortran, Tcl, Perl, and Python. IFEFFIT supports XAFS analysis procedures, Fourier transforms, and FEFF calculations, as well as data plotting and algebraic manipulation. The library is designed to be flexible and programmable, allowing users to create and save macros for repetitive tasks. IFEFFIT uses the PGPLOT graphics library for plotting and can be built without built-in graphics. It is available under an Open Source license and is still in development, with plans to add advanced features like simultaneous fitting of multiple datasets and improved background refinement. G.I.FEFFIT, a graphical user interface for IFEFFIT, provides a user-friendly environment for data analysis and plotting.