Mesh simplification, in your browser

retop reduces the triangle count of STL files for 3D printing, game assets and quick visualization — without ever uploading your file.

Why simplify?

STLs exported from CAD tools, 3D scanners or sculpting apps often have far more triangles than needed. A 2M-triangle model slices just as well as 200K for most FDM prints, but takes 10× longer to open, upload to a slicer, or render in a viewer.

For game assets, mobile 3D or AR, the overhead is worse — every extra triangle costs GPU time.

How it works

retop uses an iterative edge collapse algorithm. For each pair of connected vertices, it computes a cost of merging them (based on how much the surface shape would change), then collapses the cheapest pair. Repeat until the target count is reached.

The implementation is from the SimplifyModifier in three.js, based on Melax's quadric error metric approach. Runs on the main thread for files up to ~500K triangles; larger files may need a few seconds.

Supported formats

• Input: STL (ASCII or binary)
• Output: Binary STL (smaller files)

Workflow

• Drop file → preview with original triangle count
• Set target ratio (5%–99%) or pick a preset
• Click Simplify → preview the result
• Toggle between original and simplified for comparison
• Download the optimized STL

Limits

• Files above 200 MB may freeze your browser tab
• Normals are recomputed from scratch after simplification
• Does not preserve texture coordinates (STL has none)
• Not suitable for topology-critical models — use MeshLab or Blender with manual control for those

What next

• Multi-file batch (coming)
• GLB/OBJ input/output
• Target by max triangle count instead of ratio
• Quality-preserving decimation using meshoptimizer WASM

Questions or wishes: hi@retop.app