A feasibility study can pull in dozens of layers: zoning context, aerial imagery, survey data, and a drawing layer for every scheme you test. Every layer in the Layers panel is something Giraffe has to load, render, or compute. Clearing out layers you no longer need keeps a project fast, not just tidy.
See Organize Layers for grouping, reordering, and renaming. This article is about removing what you don't need, not organizing what you keep.
Hiding a layer doesn't speed anything up
The eye icon only sets a layer's opacity to 0. Giraffe still keeps the layer mounted and still loads its data. If you're not using a layer, remove it instead of hiding it.
Remove data layers you're no longer using
Right-click a data layer (zoning context, aerial imagery, survey files, anything added from the layer library) and choose Remove from project. Giraffe stops fetching and rendering that layer's data for this project entirely. The layer isn't deleted. It stays in your layer library for the next project that needs it.
Delete draw layers you were only using to test something
Testing a massing option or a design alternative often means a throwaway drawing layer. Delete it once you've picked a direction instead of leaving it in the project. A drawing layer with nothing on it is labeled (Empty) in the list, so you can spot leftover test layers at a glance.
Right-click a layer, or select several with Shift or Ctrl/Cmd click, and choose Delete. Deleting more than one layer at once relabels the option Delete N layers. Giraffe warns you if a layer still has features on it, so you know what you're about to lose.
See Project Cleanup to bulk-delete every empty draw layer in the project at once, along with unused usages, flows, blocks, scenarios, and properties.
Every feature counts toward your project's size
Geometries left over on unused draw layers still count against Giraffe's per-project limits and still factor into every recompute. See Improve Project Performance for the specifics on project size limits.