Docs
Docs & FAQ
How Meshdiff's comparison actually works, what's supported, and what happens to your files.
How do I compare two STL files?
Open the free diff tool (or the dedicated /compare-stl-files page), drag your "before" file into the Version A slot and your "after" file into Version B, then run the comparison. Meshdiff voxelizes both meshes into a shared grid and highlights added geometry in green and removed geometry in red, with an optional surface-heatmap layer showing dimensional drift.
What is voxel diffing?
Voxel diffing divides the 3D space both models occupy into a shared grid of small cubes (voxels), then classifies each voxel as added (occupied in Version B but not A), removed (occupied in A but not B), or unchanged. It's the same underlying idea as volumetric CSG, but Meshdiff uses it purely for comparison and visualization — it never produces a merged output mesh, and it never runs a boolean operation on the original geometry.
What file formats are supported?
STL, 3MF, and OBJ, all parsed natively in your browser with no server-side conversion step. STL and OBJ assume millimetre units; 3MF units are read from the file itself.
Is my file ever uploaded anywhere?
In the free Community tool, no — comparing or measuring a model happens entirely in your browser, and the files never leave your machine. The one exception is creating a share link, which uploads both files directly to storage (not through Meshdiff's own servers) so the recipient can view the same comparison. Pro and Team plans upload files to storage by design, since they provide saved projects, version history, and team review.
What does dimensional drift mean?
Dimensional drift is how far a surface has moved between two versions, measured point by point rather than as a single bounding-box number. Meshdiff computes it with a per-vertex signed-distance field: for each point on one surface, it finds the nearest point on the other and records the signed distance — positive where the surface pushed outward, negative where it pulled inward — then renders that as a color gradient (heatmap) over the model.
What do the Free, Pro, and Team plans include?
The comparison engine — voxel diff, surface-heatmap drift, measuring, and shareable links — is free forever on the Free (Community) plan, no account required. Pro adds saved project workspaces, version history for every model, and PDF diff reports. Team adds comment pins on 3D models, a team approvals workflow, and print-log tracking (slicer profile snapshots, print-result photos) per version. See the full feature comparison.
What happens to my saved comparisons if I downgrade from Pro?
Your existing projects, versions, and comments are retained — nothing is deleted. You keep read access to all of it: viewing a project, its version history, its diffs, and its comments still works. Adding anything new — uploading a version, commenting, approving/rejecting, deleting a version, or attaching a slicer profile or print photo — requires resubscribing to Pro or Team.
Is there a limit to file size or number of comparisons on Free?
No comparison limit — compare as many files as you want, as often as you want. File size isn't capped by us either: parsing and voxelizing happen entirely in your browser, so the practical ceiling is whatever memory your browser tab has available, not a number we impose. (Saved projects on Pro and Team are a separate case: uploads there go to server storage, which is capped at 50MB per file.)
Still have a question? Email support@projscope.com, or see the roadmap and changelog.
Ready to see what changed?
Drop two files into the free diff tool — no account, nothing leaves your browser.
Open the diff tool