ShelXle is a graphical user interface (GUI) for SHELXL, the most widely used program for small-molecule structure refinement. It combines an editor with syntax highlighting for .ins (input) and .res (output) files with an interactive 3D visualization of the structure, including electron density (F_o) and difference density (F_o-F_c) maps. Key features include intuitive atom (re-)naming, a strongly coupled editor, structure visualization in various mono and stereo modes, and a novel way of displaying disorder over special positions. ShelXle is fully compatible with SHELXL, written in C++ using Qt4 and FFTW libraries, and is available free of charge for Windows, Linux, and Mac-OS X. The SHELX programs, originally developed in the 1970s, were designed for use with photographic intensity data and punched cards. Today, SHELXL is still widely used for small-molecule structure refinements, despite the availability of modern GUIs. ShelXle was developed to provide a simple, intuitive, and robust GUI that retains the original SHELX features and capabilities. ShelXle opens a SHELX-format .res file and displays it in an interactive editor window alongside a 3D visualization. The editor uses color highlighting to identify selected atoms and syntax errors. Clicking on an atom in the visualization moves the text cursor to the corresponding atom in the editor. The GUI is controlled by menus and toolbars, with no command-line input required. ShelXle supports electron density maps, including F_o and F_o-F_c maps, visualized as mesh-style isosurfaces. Q peaks, or difference electron density maxima, are visualized as color-coded icosahedra. The editor includes syntax highlighting and code-word completion, allowing users to input SHELXL commands efficiently. It also provides a refinement history feature, storing each refinement step and allowing users to revert to previous steps if needed. ShelXle also includes an information window that displays hydrogen bonds, distances, angles, and other structural details. It allows users to label and rename atoms, with options to tie occupancies to free variables. The program also provides functions for adding hydrogen atoms, handling disordered molecules, and performing other tasks to expedite structure refinement. ShelXle is available free of charge for most modern Windows, Linux, and Mac-OS X systems. It is designed to be user-friendly, efficient, and compatible with SHELXL, making it a valuable tool for crystallographers.ShelXle is a graphical user interface (GUI) for SHELXL, the most widely used program for small-molecule structure refinement. It combines an editor with syntax highlighting for .ins (input) and .res (output) files with an interactive 3D visualization of the structure, including electron density (F_o) and difference density (F_o-F_c) maps. Key features include intuitive atom (re-)naming, a strongly coupled editor, structure visualization in various mono and stereo modes, and a novel way of displaying disorder over special positions. ShelXle is fully compatible with SHELXL, written in C++ using Qt4 and FFTW libraries, and is available free of charge for Windows, Linux, and Mac-OS X. The SHELX programs, originally developed in the 1970s, were designed for use with photographic intensity data and punched cards. Today, SHELXL is still widely used for small-molecule structure refinements, despite the availability of modern GUIs. ShelXle was developed to provide a simple, intuitive, and robust GUI that retains the original SHELX features and capabilities. ShelXle opens a SHELX-format .res file and displays it in an interactive editor window alongside a 3D visualization. The editor uses color highlighting to identify selected atoms and syntax errors. Clicking on an atom in the visualization moves the text cursor to the corresponding atom in the editor. The GUI is controlled by menus and toolbars, with no command-line input required. ShelXle supports electron density maps, including F_o and F_o-F_c maps, visualized as mesh-style isosurfaces. Q peaks, or difference electron density maxima, are visualized as color-coded icosahedra. The editor includes syntax highlighting and code-word completion, allowing users to input SHELXL commands efficiently. It also provides a refinement history feature, storing each refinement step and allowing users to revert to previous steps if needed. ShelXle also includes an information window that displays hydrogen bonds, distances, angles, and other structural details. It allows users to label and rename atoms, with options to tie occupancies to free variables. The program also provides functions for adding hydrogen atoms, handling disordered molecules, and performing other tasks to expedite structure refinement. ShelXle is available free of charge for most modern Windows, Linux, and Mac-OS X systems. It is designed to be user-friendly, efficient, and compatible with SHELXL, making it a valuable tool for crystallographers.