Frequently asked questions
Quick answers about Preview3D. Missing something? get in touch.
Do I need to install anything else for Quick Look previews and Finder thumbnails?
No. The Quick Look and thumbnail extensions are bundled inside the app and register automatically when you install it from the Mac App Store - they're enabled by default, nothing to turn on. You may need to launch the app once (or relaunch Finder) before thumbnails start appearing.
Will Preview3D take over as the default app for my 3D files?
No - by design. Preview3D appears under Open With but doesn't hijack your existing default, so your slicer or CAD app stays in charge. To make it the default for a type, use Get Info → Open With → Change All. For formats no other app handles (e.g. STEP), it opens them directly.
Which formats can it open?
STEP / STP, STL, OBJ, PLY, glTF / GLB, USDZ / USD, COLLADA (DAE), and 3MF - including painted multi-material prints - plus FBX, 3DS, X3D, LWO and more via Assimp.
Does it need an internet connection? Does it collect any data?
No. Everything runs on your Mac and your files never leave the device - no analytics, no accounts, no tracking. The only network use is an optional check for a newer version. See the Privacy Policy.
Does it run on Intel Macs?
Preview3D is Apple Silicon only (M-series). It requires macOS 14 Sonoma or later.
Can it edit or repair models?
No - it's a viewer and converter (read-only). It renders, measures, inspects (including STEP PMI / GD&T) and converts, but never modifies your source geometry.
How does it show STEP files in color and as separate parts?
It reads STEP with StepKit, a pure-Swift B-rep kernel that tessellates the exact geometry into a watertight, smooth-shaded mesh - App-Store-clean and fast. Assemblies show as a part tree you can click to highlight and isolate, and files that carry STEP colors (STYLED_ITEM) render each part in its assigned color.
Is STEP support final?
STEP viewing is currently in beta. Most files render great, but StepKit is a young pure-Swift B-rep kernel and some complex geometry may not tessellate perfectly yet - it's improving with every release. STL, OBJ, 3MF, glTF and the other mesh formats are fully supported.
Are the measurements and conversions accurate enough for manufacturing?
Volume, surface area and conversions are produced by automated tessellation and are great for a quick check - but always verify against your authoritative CAD source for manufacturing-critical work.
Another app shows the Quick Look preview for my STEP files - why?
Another installed 3D app may declare the same file type and win the preview. Removing that app, or setting Preview3D as the default for the type, hands previews back to Preview3D.
Is it a one-time purchase?
Yes - Preview3D is a one-time purchase on the Mac App Store. No subscription.