is there an app that lets you build lego?

If you want to design your own models

BrickLink Studio is digital brick building software for Windows and Mac, powered by the LEGO Group. You get snap-to building with unlimited bricks, an instruction maker for custom, print-ready instructions, and a photorealistic renderer, with BrickLink integration so you can buy the parts for whatever you have made. You can edit steps and pages of your instructions inside Studio. Its download page states no price, so we have not listed one.

The catch is the setup. It is a desktop download, not a phone app, and its page says it only supports Nvidia graphics cards at the moment. It also needs 64-bit Windows 10 or newer or macOS 10.13 or newer, 1GB RAM and 2GB of space. If your computer has a different graphics card, check that page before you get attached to the idea.

If you do not want to install anything

Mecabricks is a website for building and rendering 3D LEGO models online, with no plug-in and no installation. Everything happens in your browser, so your work is available anywhere, and there is a library of thousands of community models to look through.

What you give up is certainty. Its homepage states no price, and we did not check what signing up adds. If you need an instruction maker or a parts-buying link, those are what the Studio page describes, and the Mecabricks homepage we read did not mention them.

If you are building a set you bought

LEGO Builder is the official LEGO building instructions app, free on the UK App Store. Its instructions are 3D and step by step, and you can zoom and rotate them. There is also Build Together, for splitting a set among several builders.

That is its whole job. It guides you through official sets and is not for designing your own models. It is on iOS and on Google Play for Android; LEGO's own page for it blocked our request.

If you have a box of loose bricks

Brickit is a brick scanner app. You scatter your bricks, take a photo, and it shows hundreds of ideas for what to build, plus where each piece is. Pick a part and it highlights where that part is in your photo, and it recognises individual parts, which also answers the question of whether an app can identify LEGO pieces. It runs on iOS, and its homepage links to Android on Google Play.

It is not an official LEGO product. Brickit says it was created by fans, and that the LEGO Group does not sponsor, authorise or support it. Its advanced features need Brickit Pro, so the free download only takes you so far.

When paying is worth it

LEGO Builder is free, and Brickit's basic scanner is free to download. The paid option here is Brickit Pro, which adds advanced scanning, building and organising features, from £5.99 a month on the UK App Store. If you scan a big collection regularly and want those extras, Pro is the upgrade to look at. If you only want ideas for a pile of bricks now and then, start with the free download.

For Studio and Mecabricks, neither page we read gave a price, so we cannot tell you whether either costs anything.

The other trade-off is official versus your own. LEGO Builder is official but only guides you through sets, while Studio and Mecabricks are for your own designs.

Brickit Pro subscriptions renew automatically unless you turn off auto-renewal at least 24 hours before the period ends. The UK App Store lists several Pro options: £5.99 or £6.99 a month, and yearly options at £34.99, £39.99, £44.99 and £59.99, plus a separate Scanner Pro at £32.99 a year, so look at which option you are choosing before you confirm.

Studio and Mecabricks do not state a price on the pages we read. That does not mean they cost anything; it means we cannot tell you, so check before you rely on either for a project you care about.

Studio's Nvidia-only note is the one most likely to stop you at the start, so read its system requirements before you download it.