Open STEP, IGES, DXF & STL files on Android — one free app, no uploads
PartLens opens the CAD files manufacturing actually exchanges — STEP/STP, IGES/IGS, DXF and STL — on Android, for free, entirely on the device. Measurement and section views work across formats, and the app tells you honestly when a format (like STL) can only support approximate numbers.
Every CAD format answers a different question. STEP carries exact solids, DXF carries 2D drawings, STL carries 3D-print meshes, IGES carries thirty years of legacy surfaces. If your phone is where files arrive, you want one viewer that handles all four properly — and is honest about the difference between them. Here's the field guide.
STEP / STP — the one that matters
The ISO 10303 exchange format: exact boundary-representation solids with true surfaces, edges and assembly structure, exported by every serious CAD system. If you can request one format from a customer, request STEP. PartLens parses it on the phone — Part-21 text in, exact geometry out — preserving assemblies, authored colours and units, and measuring with exact/approximate honesty. Start with how to open STEP files on Android if that's your file.
IGES / IGS — the legacy workhorse
Older than STEP and looser about what it stores (often surfaces rather than watertight solids), IGES still flows out of legacy tooling libraries and older suppliers daily. PartLens reads the commonly-exchanged IGES entity set on-device, free — so an .igs in the inbox is a tap, not an excuse. Expect surface models: gaps between faces are the format's nature, not a bug in the file.
DXF — the 2D drawing on your phone
Profiles for laser and wire-cut, flat patterns, hole layouts: DXF is how 2D still travels. PartLens renders lines, polylines, circles, arcs, ellipses and splines as a crisp wireframe, reads the file's declared units ($INSUNITS), and keeps snapping exact — circle centers stay true centers, so a hole pitch off a DXF is a real number, not a guess against rasterised linework. DWG is a different, proprietary story: we deliberately don't parse it on the device — export DXF from the source, or convert on a PC.
STL — fine for shape, weak for numbers
STL is a bag of triangles: perfect for 3D printing, poor for inspection, because the format has no exact edges, circles or units. PartLens opens STL for exactly what it's good at — checking shape, orientation and printability — and tags its measurements approximate ≈, because on this format, that's the truth no matter which app you use. If a STEP of the same part exists, measure the STEP.
.partlens — heavy assemblies, instant open
For monster files, the free Windows PartLens Converter pre-tessellates and indexes a STEP once on your PC and emits a .partlens package that opens near-instantly on the phone — the expensive work happens one time, on the machine that has the horsepower. 100% local, no account, no upload.
Format cheat-sheet
| Format | What it carries | Best for | Measurement honesty |
|---|---|---|---|
| STEP / STP | Exact solids + assemblies + colours | Everything — request this | Exact ✓ available |
| IGES / IGS | Surfaces, legacy geometry | Older suppliers, tooling libraries | Exact on clean entities |
| DXF | 2D drawing entities | Profiles, flat patterns, hole layouts | Exact snap on true centers |
| STL | Triangle mesh only | 3D-print checks, rough shape | Approximate ≈ by nature |
| .partlens | Pre-tessellated STEP package | Huge assemblies, instant reopen | Inherits STEP exactness |
Frequently asked questions
What's the best app to open IGES files on Android?
PartLens opens IGES/IGS free and offline. Glovius also reads IGES within its subscription. Most basic free viewers don't handle IGES at all.
Can I open DWG files on Android with PartLens?
No — DWG is a proprietary format and we chose not to ship a half-correct reader. Export DXF from the source CAD (every tool that writes DWG also writes DXF) and open that instead.
STEP vs STL — which should I ask a customer for?
STEP, always, unless the file is only for 3D printing. STEP carries the exact geometry; STL is a lossy mesh of it. You can always make an STL from a STEP — never the reverse.
Do all these formats work offline?
Yes. PartLens parses every supported format on the device and has no INTERNET permission, so nothing you open can leave the phone.
One app for the files your inbox actually receives
STEP, IGES, DXF, STL — opened free and offline, measured honestly. PartLens is in Google Play closed testing now.
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