G-Code Modifier

A browser-based G-code editor and print analyzer for 3D printing. Inspect layers in 3D, simulate prints, detect potential failures before they happen, and modify G-code — all without installing anything.

Try it live — no download required.

Features

3D Visualization — WebGL layer viewer with motion-type coloring, travel moves, and interactive camera	Print Analysis — Thermal simulation, structural analysis, and motion kinematics with 12 heatmap overlay modes
Warp Prediction — 3D warp mesh with material-aware failure prediction and adjustable deformation preview	Hole Detection — Scan all layers to find holes, calculate insert depths, and auto-add pauses
Print Simulation — Move-by-move playback with speed control and automatic pause detection	Edit Mode — Select, edit, or delete individual G-code moves directly in 3D with live preview
Layer Modifications — Pauses, filament changes, Z-offsets, eject sequences, recovery, and custom G-code	G-code Reference — 40+ commands with firmware-specific notes and click-to-insert

Getting Started

1. Open the live version or open gcode-modifier.html locally (WebGL2 required)
2. Select your firmware from the dropdown (Bambu Lab, Klipper, Marlin, RepRapFirmware)
3. Drop a .gcode / .gco / .g file onto the page
4. Browse layers, run analysis, add modifications, and export

Slicer Compatibility

PrusaSlicer exports binary G-code by default. Uncheck the binary option in preferences to export plain .gcode.

For Developers

Source lives in src/ as ES modules. A zero-dependency build script inlines everything into a single gcode-modifier.html.

node build.js            # build
node --test              # run tests

Edit files in src/, not gcode-modifier.html directly. Run both commands before committing.

Documentation

• User Guide — detailed feature documentation, keyboard shortcuts, firmware profiles
• Analysis Theory — thermal model, structural analysis, motion kinematics
• DISCLAIMER.md — safety notice and liability

License

MIT — see DISCLAIMER.md for safety and liability terms.