G-code Viewer

The G-code Viewer shows exactly what a sliced file will print. It also tracks a running print live, building the model bead by bead by following the actual toolhead path, not an interpolated position between telemetry updates.

The viewer is built for large files. A 100 MB file starts rendering in about a quarter of a second and keeps filling in while the rest of the file downloads and parses. You can orbit and inspect the model before it finishes loading.

Opening a file

The Load G-code card lists the files on the printer, newest first. Type to filter the list. Select a file and choose Load.

Two shortcuts save you a search:

• Load current print: Jumps to the file for the job currently printing.
• Open local file: Loads a file from this device without uploading it to the printer. Use it to check a slice before committing to it.

A file over about 150 MB asks for confirmation before loading, since rendering it uses significant memory on your device. Files above 4 GB are rejected.

Following a live print

Follow live toolhead tracks the job Klipper is currently printing. It follows the actual moves in the file instead of interpolating between position reports, so corners stay sharp and the marker never cuts across a curve.

Geometry ahead of the current print position is not drawn. Only what has printed is shown, so the model's edge always matches real progress. Finished layers show in the printed color.

This feature requires that the loaded file matches the file being printed. The viewer checks this automatically and falls back to plain position tracking if it cannot confirm a match, or if the job data becomes inconsistent. Following the toolhead trails the actual printer position by a couple of seconds; this delay provides enough known path ahead to draw the motion continuously.

Reduced-motion settings replace the continuous path with discrete position updates.

Inspecting the toolpath

Color changes how moves are colored:

• Single: One color for the whole model.
• Feature: Colors each move by its type: external and inner perimeters, infill, solid infill, bridges, support, skirt, and brim. The legend lists only the types present in the file. A file from an unrecognized slicer shows its moves as unclassified.
• Feed rate: Shades moves from slow to fast based on the extrusion speeds in the file. Use it to find where the slicer reduced speed.

Highlight seams marks where each extrusion path starts and stops: the points where a seam can appear on the print.

Layers and cross-sections

The Visible layer slider sets the top layer shown. Lowest visible layer sets the bottom layer shown. Raising the lowest layer cuts a horizontal slice out of the middle of the print. Set both sliders to the same value to inspect a single layer, or raise the lowest layer to see inside a solid object.

Show travel moves draws the non-printing moves between extrusions. Use it to spot stringing across the model's surface.

Moving the view

Drag with the left mouse button to rotate the model. Drag with the right or middle button to pan. Use the scroll wheel to zoom. Zooming centers on the point under the pointer. Rotation pivots around the point you are looking at, so a detail stays in view while you inspect it.

Double-click, or press 0, to reset the view to the full model. Arrow keys pan the view. Shift with the arrow keys rotates it. + and - zoom.

On a touchscreen, one finger orbits the model, the same as a left-button drag. Two fingers switch to panning and pinch-zoom, the same gesture used on the bed mesh map.

The chips in the corner of the view zoom, reset the framing, and save a screenshot of the current view. The gear icon opens two settings:

• Rotation pivot: Sets whether rotation happens around the center of the view or the point under the pointer.
• Snap to center: Moves the point you grabbed to the center of the view as you start rotating.

Replaying a file

Start simulation plays the file from the beginning at the speeds specified in the file, at up to 20×, with a scrubber to jump to any point. Simulation works without a printer connected. Use it to read a slice, check where a long print spends its time, or find a problem before printing it.

During simulation, the selected color mode still applies: printed geometry keeps its feature or feed-rate color, and the rest of the model shows as an outline shell.

Rendering quality

Rendering quality defaults to Auto. Auto measures the actual frame time on your device and adjusts the level of detail to keep the view responsive. It reduces geometry detail first, then sharpness. The active layer of a running print always renders at full precision, regardless of zoom level.

Quality renders at the highest detail level. Use it for screenshots. Performance starts at the lowest detail level and increases it as the device allows. Performance also renders extrusions as squares instead of rounded shapes. This roughly doubles the frame rate when orbiting close to a large model, and gives a zoomed-out model a calmer, more solid look, since square extrusions have no curved surface to catch light. On a phone or a Raspberry Pi's browser, use Auto or Performance mode to keep the view responsive.

Narrow screens

Below roughly 55 rem, the controls stack above the view and the page scrolls as a single column. The viewer is available from the overflow menu instead of the bottom bar, since it uses more device resources than a page suited to a permanent slot.