Free Online G-code Viewer (No Signup)
Also opens DWG, DXF, STEP, IGES, IFC, SKP, STL, OBJ, GLB, FBX, 3DM and other 3D/CAD files. Drop any file on the viewer.
Works directly in Chrome, Firefox, Safari, and Edge
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What Is a G-code File?
G-code is the language machine controllers read. Each line is a command made of words, a letter and a number: G1 X20 Y10 E0.5 moves in a straight line to X 20, Y 10 while pushing 0.5 mm of filament, G2 and G3 cut arcs, and M104 S210 heats a nozzle. A slicer such as Cura, PrusaSlicer, Bambu Studio or OrcaSlicer writes it for a 3D printer as a .gcode file, and CAM programs such as Fusion, VCarve or Mastercam write it for mills and routers, often as .nc, .ngc or .tap.
The viewer reads the program the way the machine would: millimetre and inch units, absolute and relative moves, position resets, homing, arcs given by their centre or radius, helical moves and drilling cycles. Every move becomes a line, coloured by its height so each printed layer or cutting depth stands out, and the moves are grouped into layers you can show or hide: the slicer’s feature types for a print (outer wall, infill, support and so on), each tool for a CNC program, and the travel or rapid moves on a layer of their own. Files of several hundred megabytes are read as a stream.
A toolpath exports as line work, for example to DXF, DWG or OBJ, or as a picture of the view.
Who Uses G-code Files?
3D printing hobbyists and print farms check a sliced file before a long print, machinists and CNC programmers check a toolpath before it runs, and laser and plasma cutter operators check a cut job. Makers share G-code on forums and with print services; this page shows it in any browser, with no slicer or controller software installed.
Common Use Cases
- Check a sliced print layer by layer before sending it to the printer
- See where a slicer put supports, infill and walls, one feature type at a time
- Check a CNC toolpath, its depths and its rapid moves before running it
- Measure a part or a toolpath at real size in millimetres
- Bring a toolpath into CAD as DXF or DWG line work
- Send a share link that opens the toolpath in any browser
Features
Opens G-code Under Any Name
.gcode, .gco, .nc, .ngc, .tap and .cnc, and G-code under any other name, recognised by its content.
Printers, Mills and Lasers
The viewer tells a 3D printer file, a CNC program and a laser job apart, and draws each the way its machine runs it.
Coloured Layer by Layer
Every move is coloured by its height, so each printed layer or cutting depth stands out.
Feature Types as Layers
Outer wall, inner wall, infill, support, skirt and the other feature types the slicer marks, each shown or hidden in one click.
Travel and Rapid Moves
Travel and rapid moves sit on their own layer: hidden at first for a print, shown for a CNC program.
Arcs and Drilling Cycles
G2 and G3 arcs by centre or radius in every plane, helical moves and the G81 to G89 drilling cycles are followed.
Inch and Millimetre Programs
G20 inch programs are scaled to millimetres, so every toolpath opens at real size.
Large Files as a Stream
Files of several hundred megabytes are read as a stream, and the part that fits the device is drawn.
Convert to DXF, DWG or OBJ
Save the toolpath as DXF, DWG, OBJ, GLB or 3DM line work, or the view as PDF, SVG, PNG or JPG.
Nothing Is Uploaded
The file is read and drawn entirely in your browser. No account, no upload, no copy of your file on a server.
Share and Embed
Send a link that opens the toolpath in any browser, or drop the viewer into your own page with one iframe.
Compatibility & Format Notes
Machines: 3D printers (Marlin, Klipper and RepRap flavours, from Cura, PrusaSlicer, SuperSlicer, Bambu Studio, OrcaSlicer, Simplify3D and others), CNC mills and routers (Fanuc, LinuxCNC, Mach3, GRBL style programs from Fusion, VCarve, Mastercam, Carbide Create and Estlcam) and laser cutters (GRBL jobs from LightBurn and LaserGRBL). The viewer tells them apart from the file.
What is read: G0 and G1 moves, G2 and G3 arcs with I, J and K centres or an R radius in all three planes, helical arcs, G20 and G21 units, G90 and G91 positioning, M82 and M83 extrusion modes, G92 position resets, G28 homing, the G81 to G89 drilling cycles, tool changes, and the slicer’s feature, layer and print time comments.
Layers: for a print, one layer per feature type the slicer marks, plus Travel moves, which starts hidden; for a CNC program, one layer per tool plus Rapid moves; for a laser job, Laser cuts plus Rapid moves. Every move is coloured by height, from blue at the bottom to orange at the top.
Files: plain-text G-code under any of its names, or G-code under another name, which the viewer recognises by its content. Prusa binary G-code (.bgcode) opens with a notice saying how to export plain G-code. A NetCDF data file, which also uses .nc, is named as what it is.
Embed on Your Website
Add this viewer to your own site with a single line of HTML. Click Embed in the toolbar to generate an embed code, or use the snippet below with your own file URL.
Your Files Stay on Your Computer
Your G-code files are parsed entirely in your browser. Nothing is uploaded, stored, or shared unless you explicitly click the Share button. Shared files are hosted for 90 days then deleted.
Frequently Asked Questions
▶Do I need a slicer or CAM program installed?
No. The viewer reads the G-code with its own reader, in your browser. Nothing needs to be installed, and no account is needed.
▶Why are the travel moves missing from my print?
A print’s travel moves cross the part at every layer, so their layer starts hidden. Turn on Travel moves in the Layers panel to show them. A CNC program’s rapid moves start shown.
▶What do the colours mean?
Each move is coloured by its height: blue at the bottom of the part, through green and yellow, to orange at the top. Each printed layer or cutting depth gets its own shade, so the layers read apart.
▶My file is a .bgcode. Does it open?
A .bgcode is Prusa’s binary G-code, which the viewer names but does not draw. In PrusaSlicer, turn off “Supports binary G-code” in Printer Settings (General, Firmware), export again and open the .gcode file.
▶Is this G-code viewer really free?
Yes, completely free. No signup, no watermarks, no file size limits on the viewer (the optional share-link feature has a 100 MB upload cap). Built by Innerscene as a tool for architects, engineers, and designers.
▶Are my files uploaded to a server?
No. All parsing, rendering, and conversion runs in your browser — nothing is uploaded, stored, or transmitted by default. The Share button is the only feature that uploads a file, and only when you explicitly click it.
▶Can I convert to another format?
Yes. Click Export in the toolbar. A toolpath exports as line work to DXF, DWG (converted on our server), OBJ, GLB and 3DM, or as PDF, SVG, PNG and JPG. Mesh formats such as STL carry surfaces only, so a toolpath has nothing to write there.
▶Can I embed this viewer on my own site?
Yes. Click Embed in the toolbar to generate a one-line <iframe> snippet you can paste into any HTML page. You can choose whether the embed shows the viewer’s toolbar.