GCodex

Free online G-Code viewer, analyzer, simulator & editor.

What is GCodex?

GCodex is a free, browser-based G-Code viewer and CNC machine simulator. It lets you visualize, analyze, and simulate G-code toolpaths for CNC machines and 3D printers — entirely in your browser, with no file upload and no account required.

When you open a G-code file in GCodex, the entire file is read locally using the browser's FileReader API. It is parsed in JavaScript, rendered in 3D using WebGL and Three.js, and displayed in 2D using the Canvas API. Nothing is ever transmitted to any server. Your file stays on your device throughout the session and is discarded from memory when you close or refresh the tab.

GCodex was built as a faster, more feature-rich alternative to NCViewer and gcode.ws. It handles larger files, renders toolpaths more smoothly, and includes features those tools don't have — layer filtering, a full analytics dashboard, an in-browser G-code editor with Find & Replace, model scaling with bounding box, and export to eight different file formats.

Features

GCodex has six main tabs, each serving a specific purpose:

• 3D View — WebGL-powered toolpath visualization using Three.js. Orbit with left mouse, pan with right mouse, zoom with scroll wheel. Camera presets for Top, Front, Side, and Isometric views. Toggle between perspective and orthographic projection. Visibility toggles for extrusion, travel, and retract moves.
• 2D View — Flat top-down layer map rendered with the Canvas 2D API. Color-coded extrusion paths per layer with gradient shifts across layers. Grid overlay for scale reference.
• G-Code Tab — Full syntax-highlighted code view with line numbers. Enable Edit Mode to modify G-code directly in the browser. Find & Replace, strip all comments, normalize whitespace, and undo support. Click Apply to immediately re-render the 3D view with your changes.
• Analysis Tab — Dashboard showing total layers, extrusion move count, travel moves, retractions, total distance in mm, and estimated print time. Per-layer extrusion bar chart. Command frequency breakdown showing the most-used G and M codes.
• Convert Tab — Export your loaded G-code to eight formats: .gcode, .nc, .stl, .obj, .svg, .csv, .json, and .txt. All conversion happens locally — no server processing. Also links to recommended slicers (Cura, PrusaSlicer) for STL-to-G-code workflows.
• Help & FAQ Tab — Inline documentation, FAQ accordion, Arduino and GRBL guides for Uno, Nano, and Mega, G-code command reference, and a feature comparison table against NCViewer and gcode.ws.

Supported Machines & Firmware

GCodex works with all standard G-code generated by any slicer or CAM software:

• FDM 3D Printers — Marlin, Klipper, RepRap, Smoothieware, Duet/RepRap Firmware. Covers Prusa, Creality, Bambu Lab, and Voron machines.
• CNC Machines — GRBL (Arduino-based routers, mills, laser cutters), LinuxCNC, Mach3, Mach4, and standard FANUC-dialect G-code.
• Bioprinters — Supports syringe extrusion G-code for calcium alginate, hydrogel scaffold printing, and other bioprinting applications. Includes a built-in bioprinting scaffold sample file.

Supported commands include G0, G1, G2, G3, G4, G20, G21, G28, G29, G90, G91, G92, M82, M83, M104, M109, M106, M107, M140, M190, and more.

GCodex vs NCViewer

NCViewer is the most widely known browser-based G-code viewer and ranks highly for the keyword "gcode viewer". However, its feature set is limited. GCodex was built specifically to be a better alternative.

NCViewer has a basic 3D and 2D viewer, no analytics, no layer filtering, no editor, no export options, and minimal documentation. GCodex adds layer filtering with real-time 3D and 2D update, a full analytics dashboard with per-layer charts, an in-browser editor with Find & Replace and undo, model scaling with bounding box, eight export formats including STL and OBJ, toolpath animation, Arduino and GRBL guides, and bioprinter support.

Contact

For bug reports or feature requests, open an issue on the GitHub repository. For privacy-related questions, see the Privacy Policy. For usage questions, see the FAQs.

Website: gcodex.tech

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