NC Viewer

NC Viewer is a browser-based CNC verification tool used to visualize and simulate CNC machining programs. Developed and maintained as a free community resource, it allows engineers and machinists to upload G-code files and preview how a machine will execute a program before it runs.

Instead of sending CNC code directly to a machine and risking costly errors, users can load a program into NC Viewer to inspect toolpaths, verify machining operations, and identify potential mistakes in a zero-risk environment. The platform reads standard G-code instructions and converts them into an interactive three-dimensional toolpath visualization, helping programmers understand how the cutting tool will move, detect programming issues, and confirm that the machining process behaves as expected.

Because it runs entirely in a web browser with no installation required, NC Viewer has found wide adoption among CNC programmers, machinists, educators, and hobbyists who need a fast, friction-free way to check G-code without opening a full CAM environment.

Key Features

• 3D toolpath visualization from G-code and NC files directly in the browser without installation or account creation
• Bidirectional code-to-path linking that highlights the corresponding toolpath when clicking any line of code, and vice versa
• Line-by-line stepping for manual program walkthrough and systematic debugging
• Rapid move visualization that distinguishes cutting moves from rapid positioning moves by color
• Coordinate origin indicator for workpiece setup reference
• View cube and manual orbit controls for examining the toolpath from any angle
• Automatic browser caching for offline use after the first visit
• Mobile-friendly interface that works on tablets and smartphones without a dedicated app

Best For

CNC programmers, machinists, and educators who need a fast, zero-friction way to visualize and verify G-code before running it on a machine. Particularly useful for manually edited programs, externally sourced NC files, and quick spot checks where launching a full CAM environment would be disproportionate to the task.

Well suited to training environments where students and new programmers benefit from seeing the relationship between code lines and toolpath geometry in real time.

Who It's Not For

Programmers who need full machine simulation with collision detection, tool and holder representation, stock material removal verification, or machine-specific kinematic modeling. NC Viewer visualizes toolpaths; it does not simulate the physical machine or its mechanics.

For production-level verification where a crash or scrapped part would be genuinely costly, a full machine simulator inside Mastercam, PowerMill, Vericut, or Fusion is the appropriate tool. NC Viewer is a quick inspection aid, not a replacement for production simulation.

Platform

Fully browser-based. Runs in any modern browser on Windows, macOS, Linux, Chromebook, and mobile devices with no installation or account required. Cached automatically for offline use after the first visit.

Pricing

Completely free. No account required, no subscription tiers, and no feature limits behind a paywall. The tool is maintained as a free community resource by its creator.

Pros

• Completely free with no registration, no limits, and no paywalled features
• Zero installation required, works in any modern browser including on mobile and tablets
• Bidirectional code-to-path navigation makes program debugging fast and intuitive
• Offline capable through automatic browser caching after first use
• Instant to use with no project setup, file management overhead, or onboarding required

Cons

• No machine-specific kinematic simulation and no modeling of tool, holder, fixture, or stock geometry
• No collision detection or material removal verification for production-level safety checking
• Limited G-code dialect support means some machine-specific codes and macros are not recognized
• No multi-axis simulation beyond basic 3-axis toolpath visualization
• Single-developer project where development pace and long-term maintenance depend on one person

Rating

⭐ 4.2 / 5

Editorial Take

NC Viewer is a practical lightweight tool for quickly inspecting and verifying CNC programs. For programmers who need a fast sanity check on G-code without the overhead of a full CAM environment, it delivers exactly what it promises with no setup and no cost.

Alternatives

CAMotics, NCnetic Viewer, G-Wizard Editor, Fusion 360 Machine Simulator, Vericut, CIMCO Edit

Used In

• CNC programming verification and pre-run inspection

• G-code education and machining training programs

• Shop floor program review and manual code editing

• Hobbyist and maker CNC projects

• Post-processor development and validation

Founded

2018