Gcode Viewer for 3D printer files
A Gcode Viewer lets you inspect the motion file your printer will actually run. STL files describe shape, but Gcode describes the machine instructions: coordinates, extrusion, travel moves, temperatures, fans, retractions, and layer changes.
Use this free Gcode Viewer when you want to preview Gcode online before moving it to a printer. The file is opened in your browser, parsed locally, and drawn as an orbitable 3D layer-by-layer toolpath preview. Nothing is uploaded.
What this Gcode preview shows
The viewer reads common G0 and G1 movement commands, tracks absolute and relative positioning, follows absolute and relative extrusion modes, detects layer changes, and separates extrusion moves from travel moves. You can orbit around the print, preview a single layer, or view all paths through the selected layer.
It also extracts practical print information from the uploaded file: layer count, printable XY and Z bounds, extrusion length, travel distance, retractions, hotend temperatures, bed temperatures, fan speed, estimated movement time, and a rough filament weight estimate.
When to use a Gcode Viewer
Use a viewer after slicing and before printing. It is especially helpful when you want to confirm the file is centered on the bed, check that the first layer starts where expected, spot stray prime lines or purge moves, compare travel moves with extrusion paths, and estimate whether the layer count and print size match what your slicer promised.
For high-risk prints, use both this browser viewer and your slicer's native preview. A lightweight online viewer is great for quick checks, but a slicer knows more about its own firmware flavor, machine profile, acceleration model, arcs, and custom macros.