Question 1

How do I compare two STL files online?

Accepted Answer

Open STL Diff Online in your browser, drop your original .stl file in the left zone and the modified .stl in the right zone. The tool voxelizes both models, auto-aligns them, and renders a 3D diff — green for added geometry, red for removed — in seconds. No signup or upload required.

Question 2

Is the STL diff tool really free with no signup?

Accepted Answer

Yes. STL Diff Online is 100% free, with no signup, no registration, no account, and no email required to compare two STL files online.

Question 3

Are my STL files uploaded to a server?

Accepted Answer

No. The whole comparison runs in your browser inside a Web Worker. Your STL files never leave your machine — nothing is uploaded, stored, or seen by us.

Question 4

What does the STL diff actually show?

Accepted Answer

A true volumetric 3D diff. STL Diff Online voxelizes both meshes, aligns them, and computes added (B minus A) and removed (A minus B) volume. Added geometry is rendered in green, removed in red, so you can spot revisions instantly — even when triangulation differs.

Question 5

What is the maximum STL file size I can compare?

Accepted Answer

The browser-based comparison handles STL files up to 80 MB per file. Performance depends on your device — modern laptops handle 10–40 MB STLs comfortably.

Question 6

Does STL Diff Online work on Mac, Windows and Linux?

Accepted Answer

Yes. STL Diff Online runs in any modern browser (Chrome, Edge, Firefox, Safari) on Mac, Windows, Linux and Chromebooks. There is nothing to install.