Definition

A slicer usually prints one or more closed wall loops around each cross-section, then fills the remaining interior with sparse or solid patterns. Outer perimeters prioritize visible surface and dimensional accuracy; inner perimeters connect them to the interior. Top and bottom solid infill close the shell.

Infill percentage alone does not define strength. Wall count, layer bonding, print orientation, material and load direction can matter more. Feature names in G-code are commonly written as slicer comments rather than standardized machine commands, so labels differ between Cura, PrusaSlicer, OrcaSlicer and other exporters.

What matters in practice

Walls define the shell

More perimeters often add strength and sealing without making the entire part solid.

Infill has several roles

It supports top layers, connects walls and changes stiffness, time and material use.

Comments identify features

The same geometry may be labelled WALL-OUTER, External perimeter or another slicer-specific name.

Example in G-code

Slicer feature markers

;TYPE:WALL-OUTER
G1 X40 E1.2
;TYPE:INFILL
G1 X60 Y20 E0.8

The semicolon lines are comments for software; the following G1 moves are the actual machine motion.

What this viewer can show

In this viewer

The viewer maps common slicer comment dialects into normalized move types so walls, infill, support and other features can be inspected consistently. Unknown labels remain visible as source text.

Primary sources

This explanation uses firmware documentation and details visible in G-code. Your printer's settings still determine what the machine does.