Open a G-code, NC or TAP file for 3D printing or CNC, see its toolpath in 2D or 3D, play it back move by move, and read the source line behind each one. Nothing leaves your browser.
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Your G-code file is processed directly in your browser. The file is not uploaded to a conversion server.
Guide
G-code is the line-by-line command language that 3D printers, CNC mills and routers follow. A viewer reads those commands and draws the path the tool is going to take, so you can check a job before it runs.
You may also see this kind of tool called a G-code reader, visualizer or previewer. ViewGcode is a viewer only. It does not edit, generate or send G-code, and it never connects to a machine.
How to view a file
Drop a file onto the upload area, or use Browse files. The viewer opens with your file loaded.
The file is parsed in a background worker, so the page stays responsive even with large files.
Drag to rotate, scroll or pinch to zoom, right-drag to pan. Fit view returns the toolpath to the frame.
Click a path to jump to its source line, or click a line to highlight its movement.
Press play, or use the layer and movement controls, to watch the job build up move by move. What playback does and does not cover.
Reading the toolpath
Moves that push filament are drawn as extrusion, moves without it as travel. Layers come from the Z height of extruding moves, so you can check the first layer and every retraction before a long print. Full guide: 3D printer G-code viewer.
Rapids are G0, feed moves are G1, and arcs are G2 and G3. Feed is listed but cannot say whether the tool is cutting or moving through air. Tool offsets and cutter compensation are not applied. Full guide: CNC G-code viewer.
Reference
Temperature, fan and spindle commands never create movement. Unsupported commands are listed in the parser notes instead of being guessed. Dialects differ between controllers, so lines with parameters or expressions (#100, [1+2]), canned cycles (G81–G89), splines and transforms such as G51 or G68 are skipped with a warning.
Limits
It does not edit or generate G-code, estimate print or machining time, or simulate collisions, tool offsets and cutter compensation. Treat it as a way to look at a file, not as a guarantee a job is safe to run. It reads plain-text G-code up to about 150 MB, so for very large files a computer with plenty of RAM works best. If a file will not load or the preview looks wrong, see G-code viewer troubleshooting.
Good to know
No account, no installer and nothing to keep updated: open the page, drop in a file and look. Everything is processed in your browser, so your designs are never uploaded and stay on your own device. The privacy policy explains exactly what is and isn’t stored.
Your G-code file is processed directly in your browser. The file is not uploaded to a conversion server.
A browser-based tool works the same on every system: use it as a G-code viewer for Windows 10 and 11, Mac or Linux. Any current browser with WebGL will do, on a laptop, desktop or tablet. Not sure what a .nc, .tap or .gcode file is? See how to open G-code files.
Cura, PrusaSlicer, Orca Slicer, Bambu Studio and Simplify3D all export plain-text G-code that this viewer opens. It reads their layer comments, so you can step through a print layer by layer. Binary .bgcode and .gcode.3mf packages are not supported.
CNC programs often use .nc, .tap, .ngc or .cnc instead of .gcode. They are all plain text, so the viewer opens them the same way. The NC file viewer page explains what an .nc file is and how to open one.
The parser tracks positioning mode, units, the active arc plane and the last motion mode. Each move becomes straight segments (arcs are split into short chords) drawn from one WebGL buffer. The 3D view is a free camera; the 2D top view looks straight down the Z axis with a grid that adapts to your zoom.
Press play to watch the toolpath being drawn move by move at the speed you choose, or step through single moves and layers. It does not simulate material removal, collisions or machine limits. See the G-code simulator page for details.
Questions
No. Your G-code file is processed directly in your browser. The file is not uploaded to a conversion server. Reading, parsing and drawing all happen on your device.
The picker suggests .gcode, .gco, .gc, .g, .nc, .tap, .cnc, .ngc and .txt. Extensions are only hints: the viewer checks that the file contains recognizable G-code motion commands, whatever it is called.
Yes. .nc is a common extension for CNC programs, and the viewer opens it like any other plain-text G-code file, drawing rapids, feed moves and arcs. Note that .nc is also used for NetCDF scientific data. That is a different, binary format, and this viewer cannot read it.
Yes, through two inspection profiles. The viewer picks one from clues in the file (extrusion values, heater commands, spindle commands, tool changes) and you can switch it manually. The profile changes how moves are labeled and coloured; it never alters your file.
Any slicer or CAM program that exports plain-text G-code. For 3D printing it reads the layer comments written by slicers such as Cura, PrusaSlicer, Orca Slicer and Bambu Studio, and falls back to the Z height of extruding moves when comments are absent.
In practice, yes. Tools like this are also called a G-code reader, visualizer, previewer, plotter or backplot. They all read the file and draw the path it describes. ViewGcode adds playback, layer controls and a linked source list, but it does not edit your file or simulate the machine.
Not directly. Those are binary or packaged formats, and the viewer reads plain-text G-code. In your slicer, export a standard .gcode file instead.
It simulates the toolpath, not the machine. You can play the path back move by move in 2D or 3D at a speed you choose, and step through layers or single moves. It does not simulate material removal, machine limits, collisions, tool offsets or timing, so use your CAM or controller simulation for those.
It is a visual check, not a validator. Looking at the toolpath and its bounds can reveal a wrong unit, a path outside your stock or build volume, or an unexpected rapid, and the parser notes list any commands the viewer skipped. It does not check a file against a specific machine, controller or slicer.
They are calculated from the commands the viewer understood. Toolpath bounds describe where the tool moves, not necessarily the size of the finished part. The viewer does not estimate print time, machining time or material use.
Commands the viewer cannot interpret reliably (for example canned drilling cycles, splines or parameter expressions) are skipped and listed in the warnings panel. The viewer does not guess their geometry.
No. This is a viewer, not a G-code editor. You can search and inspect source lines, but nothing is edited, saved back or executed, and the tool never connects to a printer or CNC controller. To change a file, edit it in a text editor or your CAM software, then open it here again to see the result.
Files up to about 150 MB are accepted, and parsing runs in a background worker so the page stays responsive. A file is also rejected if it holds more than 2.5 million movements or would produce more than 2.5 million toolpath segments, or if the browser runs out of memory. In each case the viewer shows an error instead of a partial result.