Infill is the structure inside your part — the stuff between the walls that gives a print strength without making it solid. Pick the right pattern and density and your part is strong, light, and fast to print. Pick wrong and you waste hours of print time on infill that does nothing for you. This is the working comparison.
15% gyroid for general-purpose prints (strong in every direction, prints fast). 10% lightning for decorative pieces (fastest, lightest, but only supports the top shell). 30% cubic or gyroid for functional/mechanical parts. Above 50% infill almost never adds useful strength — thicker walls do that better.
Infill is not what holds your part together — walls do that . Infill mostly does three things: supports the top layers so they don't sag (pillowing); transmits load between top and bottom shells; and resists localised crushing. Beyond 30–40% infill density, returns diminish sharply because walls dominate the load path. For maximum strength per gram, increase wall count before infill density.
Two perpendicular sets of straight lines. The default in many slicers. Prints fast, decent strength in two axes (X and Y), weak in the third (Z). Notable downside: the nozzle has to plow through the previous line at every intersection, causing artifacts.
One set of straight lines per layer, alternating direction every layer. Simpler than grid, slightly faster, similar strength.
Three sets of lines forming triangles. Stronger than grid (triangles are rigid shapes), but slower to print because of all the direction changes.
3D cubes oriented diagonally. Strong in all three axes (the only common pattern that's truly 3D-strong from each layer), fast to print, looks neat in preview.
A 3D continuous curved surface inspired by molecular structures. Excellent strength-to-weight ratio, isotropic (strong in every direction), prints with no sharp direction changes — meaning fast travel-free toolpaths.
Classic honeycomb cells. Strong, but slow because of the many vertices.
Branching tree-like structure that only exists where it's needed to support the top layers. Uses dramatically less material than other patterns.
Concentric copies of the part outline. Smooth, decorative, used most for top/bottom layers rather than internal infill. Inside, weak.
Cubic where density adjusts dynamically — dense near the surface, sparse in the middle. Saves material on large parts without sacrificing the top-layer support.