About

This Online G-Code Viewer provides a precise, browser-based simulation of CNC and 3D Printer toolpaths. Unlike basic text editors, this tool interprets the geometric logic of G-Code, rendering moves, arcs, and rapid travels on an interactive 2D canvas.

CNC machining relies on precise coordinate systems. A standard linear move is defined as a vector from P_start to P_end. This tool calculates the Euclidean distance d = √Δx² + Δy² and renders the path with color-coded velocity states (Rapid vs. Feed).

Critical for verification, the viewer parses complex Circular Interpolation commands (G2/G3), calculating arc centers using the offset parameters I and J. It also validates the Bounding Box limits to prevent machine crashes by exceeding axis travel.

Formulas

Linear Interpolation Time (t)

t = √(x₂ − x₁)² + (y₂ − y₁)²F

Where F is the Feed Rate.

Arc Center Calculation (I, J offsets)

C_x = x_start + I

C_y = y_start + J

Reference Data

Code	Function	Type	Parameters
G0	Rapid Positioning	Motion	X, Y, Z
G1	Linear Interpolation	Motion	X, Y, Z, F (Feed)
G2	Clockwise Arc	Motion	X, Y, I, J, R
G3	Counter-Clockwise Arc	Motion	X, Y, I, J, R
G20/G21	Units (Inch/mm)	Setup	None
G90/G91	Absolute/Relative	Setup	None
M3/M5	Spindle On/Off	Machine	S (Speed)
F	Feed Rate	Parameter	Value (units/min)

Frequently Asked Questions

CNC machines often use a coordinate system where Y+ is "away" from the operator. However, screen coordinates usually have Y+ going "down". This viewer uses standard Cartesian coordinates (Y+ is Up), but if your post-processor assumes a different origin, use the "Flip Y" toggle or check your G-Code generator settings.

Yes. While it optimizes for a Top-Down (2D) view to verify XY paths, it parses Z-heights to calculate layer changes. It distinguishes between extrusion moves (G1 with E parameter) and travel moves.

The viewer uses the standard I/J incremental offset method. It calculates the center point relative to the start position: CenterX = StartX + I. If your G-Code uses "R" (Radius) format, the parser mathematically converts the Radius and Start/End points into a valid arc center.

No. The entire parsing and rendering process happens client-side in your browser using JavaScript. Your proprietary design files never leave your computer.