Preparing the PartLens preview.

PartLens Windows preview · Android on Google Play Download

PartLens · Windows + Android + macOS beta

Inspect the STEP file. Keep it off the cloud.

A free, offline CAD inspection system for Windows, Android, and Apple-silicon Macs (beta). Open STEP/STP, CATIA V5 parts and assemblies, and seven more supported families, inspect assemblies, measure with visible exact/approximate provenance, cut sections, draft views, and compare revisions.

See the Windows preview Get it on Google Play Watch the workflows↓
Windows 10/11 x64v2.31.1 · unsigned preview Androidv2.31.0 · Google Play macOSv2.30.5 · Apple-silicon beta
8import families 9display modes 7standard views Localno CAD upload .partlenspersistent projects

Product proof · shipped now

Every screen.
One inspection model.

Use the native Windows workbench at your desk, take the same local-first inspection language to an Android phone or tablet at the part — and, new in beta, run the identical workstation natively on an Apple-silicon Mac.

WINDOWS 10/11 x64 Native workstation preview Live, customer-safe walkthrough using the anonymized PartLens web model.
PLPartLens DEMO-ASSEMBLY.step LOCAL · 60 FPS
OPENASSEMBLYINSPECTMEASURE SECTIONDRAWINGCOMPARE FITISOFRONTTOP
3D VIEWPORT · PERSPECTIVE
Ø18.000BORE · EXACT ✓
NAVIGATE · SHADED WITH CAD EDGES LOCAL · OFFLINE
product treeexact sectionssaved viewpointsreports
ANDROID · GOOGLE PLAY Touch-first field viewer Actual emulator capture: the same demo file across all nine shipped display modes.
PartLens Android showing one demo CAD file in nine display modes
CAPTURED PRODUCT UI · DEMO FILE · NO CUSTOMER IDENTIFIERS
phone + tablet9 display modes7 viewsCAD stays local

01 / Inspect · shipped now

Measure the geometry.
Cut the part.

Snap to vertices, centres, edges, and faces. Measure point-to-point distance, XYZ deltas, angles, and datum-based coordinates in millimetres or inches. Analytic and retained B-rep answers stay exact ✓; mesh-derived answers remain approx ≈.

Move an X, Y, or Z plane through the model for a live section, then turn standard views, planar faces, or principal-plane cuts into persistent drawing sheets with dimensions, hidden lines, notes, layers, and DXF/PDF export. Windows also exports SVG.

magnetic snap custom datum visible provenance exact section persistent drafting

02 / Assemblies · shipped now

Understand the assembly.
Focus on one part.

PartLens preserves the STEP product structure instead of flattening it into a mesh list. Search products, subassemblies, references, occurrences, and bodies; select a branch; then fit, hide, show, explode, or isolate exactly what you chose.

Isolation hides every other occurrence and frames the selected branch. Per-occurrence visibility means one placed instance can remain hidden without hiding every copy of the same reference.

product structureoccurrence accurate branch isolatesaved visibility

03 / Compare · shipped now

See the revision
before it reaches the machine.

Load base and target files into aligned views. Revision mode identifies added, removed, and changed manufacturing features and sampled geometry regions. LH/RH mode separately checks mirrored intent instead of treating a mirror as an ordinary revision.

Match cameras, select an evidence row, and locate the corresponding region in both models. Windows exports comparison evidence to CSV for review.

auto alignmentmatched cameraslinked markersCSV evidence

Technology · shipped now

Offline by design.
Exact when it matters.

A shared Kotlin engine owns import, tessellation, assemblies, measurement, compare, drafting, projects, and reports across Android, Windows, and the new macOS beta. Responsive geometry keeps the viewport moving; retained B-rep and isolated OpenCASCADE work provide authority when the answer must be exact.

No runtime CAD cloudNo CAD upload, account, telemetry service, or cloud dependency. Only a small public version manifest is checked for updates.
Visible provenanceExact ✓ and approximate ≈ stay attached to the result, so speed never masquerades as authority.
Exact section authorityResponsive preview first, isolated OpenCASCADE linework when the authoritative answer is ready.
Persistent inspectionMeasurements, visibility, viewpoints, compare evidence, and drawing sheets persist in .partlens projects.
Nine import familiesSTEP/STP, IGES/IGS, CATIA V5 (CATPart, CATProduct), STL, OBJ, PLY, GLB/glTF, DXF, and saved .partlens projects.
One anonymized web modelThe model in these walkthroughs was tessellated by the PartLens engine, then stripped of names, PMI, and B-rep before publication.
STEP / STPIGES / IGSCATIA V5STLOBJ PLYGLB / glTFDXF.partlens

PartLens for Android · Google Play

Measure with confidence from the first tap.

PartLens for Android makes Smart Measure the obvious first path while keeping advanced inspection tools close at hand. Every safe result explains its units, witness geometry, provider, and Exact or Approximate status.

One-tap feature measurementSmart, Feature, Edge Length, and Angle modes for bores, bosses, fillets, tapers, chamfers, true arcs, and face area.
Weight & quoting propertiesEnvelope, surface area, volume, mass, centre of gravity, projected area, and stock utilisation—with closed-solid honesty gates.
Clearance & interferenceSelect two assembly parts and distinguish a clear gap, touching contact, and material clash.
Shop-language calloutsØ, THRU, BLIND, counterbore, countersink, and honest stepped-hole descriptions in the active units.
Correct report quantitiesAngles remain degrees and areas remain square units in exported reports instead of being treated like lengths.

ANDROID v2.31.0 · VERSION CODE 116 · GOOGLE PLAY

New in 2.31 · Android + Windows

Open CATIA files without CATIA.

CATIA V5 parts and whole assemblies now open in PartLens — free, offline, with no CATIA licence and no upload. Parts are shown from the display shape CATIA saves inside every file, so CATIA measurements are honestly marked approximate ≈. How the free CATIA viewer works.

.CATPart and .CATProductParts and assemblies, sub-assemblies included, each part placed where CATIA puts it.
CATIA's own treeThe parts list uses CATIA's instance names, and parts saved without a shape stay listed.
Every V5 releaseChecked on real files saved by V5R19 (2009) through V5-6R2024; anything unreadable is refused in plain words.
Assemblies on a phoneSend the assembly folder as one .zip and every part is placed. Step by step.

CATIA V5 · ANDROID + WINDOWS 2.31 · MAC BETA NEXT

New · PartLens comes to the Mac

The workstation, native on Apple silicon.

The same shared engine and desktop workbench now build and run natively on Apple-silicon Macs. Verified on an M1 Max: the viewport's exact OpenGL configuration passes its go/no-go probe, and a 209-occurrence production die opens in about a second.

Native arm64, no translationCompiled for Apple silicon; the 2.4-million-triangle reference die renders through the same instanced pipeline as Windows.
Mac-native input⌘ shortcuts, trackpad orbit/pan/zoom with measured tuning, and context clicks that follow macOS conventions.
Same projects, same provenance.partlens projects, saved viewpoints, and exact ✓ / approximate ≈ marking carry over unchanged.
Exact kernel aboardThe DMG carries a natively built OpenCASCADE 7.8.1 (141 toolkits, arm64), so exact sections and measurements match Windows — the beta remains ad-hoc-signed and by request.

MACOS v2.30.5 · APPLE SILICON (ARM64) · BETA BY REQUEST

Current public builds

Choose your PartLens.

The Windows workstation, the Android field viewer, and the new Apple-silicon macOS beta share the same local-first inspection language, but their release channels are different. The terms below are the terms of the files you can obtain today.

PartLens is a viewer and inspection tool. It never writes back to the source STEP or STP file.

ANDROID · GOOGLE PLAY

PartLens for Android v2.31

Open STEP and CATIA files and take touch-first Smart Measure, assembly inspection, analytic feature measurement, part properties, clearance checks, sections, drafting, compare, nine display modes, and seven views to the part.

  • No CAD upload or usage telemetry
  • Phone and tablet layouts
  • Feature, weight, and clearance tools
  • Free on Google Play, updates automatically
Get it on Google Play v2.31.0 · version code 116 · public on Google Play
Free download; Google Play keeps it up to date.
MACOS · APPLE SILICON BETA

PartLens for Mac v2.30 beta

The same offline inspection workstation, compiled natively for Apple silicon: assemblies, provenance-marked measurement, GPU sections, drafting, compare, and reports on the identical shared engine.

  • Native Apple-silicon build (M1–M4)
  • Trackpad-first input · ⌘ shortcuts
  • Same .partlens projects as Windows
  • Native OpenCASCADE exact kernel included
Request the macOS beta
Before you install

Beta DMGs are sent directly and are not yet notarised: on first launch, right-click the app and choose Open to pass Gatekeeper. The DMG bundles the native OpenCASCADE kernel (141 toolkits), so exact sections and measurements carry the same exact ✓ provenance as Windows.

v2.30.5 · Apple silicon (arm64) DMG · by request
Built and tested on Apple silicon · fully local
OPTIONAL WINDOWS UTILITY

PartLens Converter

Turn heavy STEP, IGES, CATIA V5, STL, OBJ, PLY, glTF, and DXF files into pre-indexed .partlens packages for faster mobile opening.

Download Converter Free Windows installer · v2.31.1 · ~38 MB · Windows 10/11 (64-bit)

Release status shown exactly: Windows is an unsigned preview; Android is free on Google Play; macOS is an Apple-silicon beta sent by request.

Guides + straight answers

Verify the workflow before you trust the viewer.

How to useCADMation NXT — your first jobInstall, open a STEP model, check the BOM, draft, balloon and export—with every unfamiliar term explained. NewA free CATIA viewerOpen CATPart and CATProduct files without CATIA — what opens, how, and the honest limits. GuideHow to open CATPart filesParts and whole assemblies on Android or Windows, plus fixes when a file won't open. GuideThe best STEP viewer for Android in 2026Every Play Store option honestly compared — price, offline use, measurement, privacy. GuideHow to open STEP files on AndroidFrom WhatsApp, email or Drive in four steps — plus fixes when a file won't open. GuideMeasure STEP files on AndroidSnapping, sections, and why exact ✓ vs approximate ≈ matters. GuideSTEP, IGES, DXF & STL on AndroidThe format field guide — what each carries and how to view it free.
Does PartLens upload CAD?No. Customer CAD stays on the phone or workstation. There is no account, telemetry service, or runtime cloud dependency.
What is actually public today?Windows v2.31 is an unsigned preview. Android v2.31 is free on Google Play. macOS v2.30 is an Apple-silicon beta sent by request.
Can PartLens open CATIA files?Yes. CATIA V5 .CATPart and .CATProduct files open free on Android and Windows (2.31), with no CATIA licence: parts are shown from the display shape CATIA saves in each file, so their measurements are approximate ≈. CATIA is a registered trademark of Dassault Systèmes; PartLens is not affiliated with or endorsed by Dassault Systèmes.
Does isolate preserve assembly truth?Yes. Select an occurrence or branch, hide everything else, auto-fit it, inspect it, then restore the saved visibility state.
Can it compare two revisions?Yes. Revision and LH/RH modes use aligned views, matched cameras, linked evidence markers, and Windows CSV export.
What does exact ✓ mean?The result came from analytic or retained B-rep geometry, or authoritative OCCT work. Mesh-derived answers remain marked approximate ≈.
Is PartLens a CAD editor?No. It is a view-and-inspect tool and never writes back to the source STEP or STP file.