For modern LEGO sets, you have two official options for building instructions: the LEGO Building Instructions mobile app, or the PDF download from lego.com. Both are free. They serve slightly different needs.
The PDF
Strengths
- Works on any device that opens PDFs — phone, tablet, laptop, e-reader.
- Can be printed for hands-free building (see how to print).
- Once downloaded, fully offline. No internet or app needed.
- Easy to save permanently — back up to your own cloud drive, share by email.
- Available for the full LEGO catalogue going back to ~1990 on LEGO.com.
Weaknesses
- Static. Pinch-to-zoom on phone is the only "interactivity."
- Multi-bag sets often span several PDFs (one per bag); you have to switch between them.
The LEGO Building Instructions app
Strengths
- Interactive 3D step-by-step for many recent sets — rotate the model, zoom into specific connections, see exactly where each piece goes from any angle.
- Step-by-step navigation with progress tracking — pick up where you left off.
- Built-in piece search — tap a piece in the diagram to see exactly which one to grab.
- Multi-bag sets unified in one interface — no switching files.
- Works offline once instructions are downloaded.
Weaknesses
- Coverage is partial. Many older sets and some recent sets aren't in the app — only the PDF exists.
- Mobile only (iOS and Android). No web or desktop version.
- Requires installing the app, which not everyone wants.
- Storage cost — the app downloads sizable instruction files per set.
Which to use when
- Building a recent flagship (Icons, large Star Wars, large Technic): the app, if available — the 3D interface dramatically helps with complex angles.
- Building a smaller modern set: either works; the PDF is faster if you're not invested in app workflow.
- Building anything pre-2015: almost certainly PDF only. The app's catalogue is mostly recent.
- Building offline / printing: PDF.
- Building over multiple sessions on different devices: PDF (saves cleanly between devices).
How to find each
- PDF →
lego.com/service/buildinginstructions→ enter set number → download. - App → search "LEGO Building Instructions" in the App Store / Play Store. Once installed, search by set number inside the app.