Preparing the PartLens preview.

PartLens Windows preview · Android closed test Download

PartLens · Windows + Android

Inspect the STEP file. Keep it off the cloud.

A free, offline CAD inspection system for Windows and Android. Open STEP/STP and seven more supported families, inspect assemblies, measure with visible exact/approximate provenance, cut sections, draft views, and compare revisions.

See the Windows preview Join Android testing Watch the workflows↓
Windows 10/11 x64v2.28.0 · unsigned preview Androidv2.27.0 · Google Play closed test
8import families 9display modes 7standard views Localno CAD upload .partlenspersistent projects

Product proof · shipped now

Two screens.
One inspection model.

Use the native Windows workbench at your desk, then take the same local-first inspection language to an Android phone or tablet at the part.

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 · CLOSED TEST 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 and Windows. 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.
Eight import familiesSTEP/STP, IGES/IGS, 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 / IGSSTLOBJ PLYGLB / glTFDXF.partlens

New in Android 2.26 · Google Play closed test

Measure a feature. Weigh the part. Check the gap.

Android 2.26 adds engineering measurements and quoting checks to the same offline viewer. Results retain exact/approximate provenance and persist with the rest of the inspection when the result is safe to save.

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 v2.27.0 · VERSION CODE 104 · GOOGLE PLAY CLOSED TEST

Current public builds

Choose your PartLens.

The Windows workstation and Android field viewer 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 CLOSED TEST

PartLens for Android v2.27

Take touch-first 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
  • Install through Google Play testing
Open Google Play testing Request a testing invite v2.27.0 · version code 104 · closed test
Already invited? Opt in on the tester page, then install through Google Play.
OPTIONAL WINDOWS UTILITY

PartLens Converter

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

Download Converter Free Windows installer · v2.19.0 · ~35 MB · Windows 10/11 (64-bit)

Release status shown exactly: Windows is an unsigned preview; Android is distributed through Google Play closed testing.

Guides + straight answers

Verify the workflow before you trust the viewer.

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 v2.28 is an unsigned preview. Android v2.27 is distributed through free Google Play closed testing.
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.