build123d
Hacker ApprovedThe most recommended of 4 code-based CAD libraries
Python CAD library that builds solid models and exports STEP files, liked for its Python-friendly design and AI coding assistant use. Common caveat: documentation is often lacking.
Python CAD library that builds solid models and exports STEP files, liked for its Python-friendly design and AI coding assistant use. Common caveat: documentation is often lacking.
62 people gave an opinion
- recommend it
- 53
- criticize it
- 9
- approval share
- 85%
Recommended in 11 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: recommended
- March 2026: recommended
- April 2026: recommended
- May 2026: recommended
- June 2026: not recommended
- July 2026: recommended
- August 2026: recommended
- September 2026: recommended
- October 2026: recommended
- November 2026: not recommended (month in progress)
Owned for 1 year
Median of the 3 owners who said how long they have had it.
Each square is one year.
Why it carries the badge
- 53 people recommend itNeeds 10 or more, met.
- 5.9 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 11 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Works well with AI coding assistants
“I've had a positive experience building a library of parametric HVAC duct parts using Claude, Gemini and Codex”
Comment from 22 May 2026 in “Antigravity 2.0 Tops the OpenSCAD Architectural 3D LLM Benchmark” “I have been using these models to make 3d models with build123d — they are great at it.”
Comment from 8 Oct 2026 in “Claude Haiku 5.5” “I model with `build123d` or `openscad` using Claude Code to do the heavy lifting”
Comment from 19 Oct 2026 in “I no longer care to work on any Ruby gems so I've archived all my repositories” - Comment from 28 Apr 2026 in “Anthropic Joins the Blender Development Fund as Corporate Patron”
- Comment from 30 Mar 2026 in “Build123d: A Python CAD programming library”
- Comment from 31 Mar 2026 in “Open source CAD in the browser (Solvespace)”
Exports STEP files
“I like build123d simply because it can export proper STEP (like CadQuery) but has a nicely python friendly design.”
Comment from 12 Sep 2026 in “Benchmark: CadQuery vs. OpenSCAD for agentic CAD work” “at least build123d (which I had never heard of, thanks!) can export STEP”
Comment from 24 Nov 2025 in “µcad: New open source programming language that can generate 2D sketches and 3D” “you can use CadQuery/Build123D and generate STEP files for some of it”
Comment from 26 Dec 2025 in “Ask HN: What skills do you want to develop or improve in 2026?” - Comment from 30 Mar 2026 in “Build123d: A Python CAD programming library”
- Comment from 17 Sep 2026 in “Benchmark: CadQuery vs. OpenSCAD for agentic CAD work”
Python-based solid (BREP) modeling
“I think it is much more capable than OpenSCAD due to BREP and Python.”
Comment from 20 Feb 2026 in “FreeCAD is an open-source parametric 3D modeler” “go straight for build123d which operates on real solid models (BREP)”
Comment from 2 Mar 2026 in “Show HN: Vibe Code your 3D Models” “something built on the open-source Open Cascade geometry kernel”
Comment from 10 Oct 2026 in “OpenSCAD the Programmers Solid 3D CAD Modeller” Better than OpenSCAD
“I've enjoyed Build123d (and it's over-loaded python operators) as an alternative to OpenSCAD”
Comment from 20 Feb 2026 in “FreeCAD is an open-source parametric 3D modeler” “I think it is much more capable than OpenSCAD due to BREP and Python.”
Comment from 20 Feb 2026 in “FreeCAD is an open-source parametric 3D modeler” “I have found better results with `build123d` than with OpenSCAD”
Comment from 11 Oct 2026 in “OpenSCAD the Programmers Solid 3D CAD Modeller” - Comment from 30 Mar 2026 in “Build123d: A Python CAD programming library”
What people warn about
Each mark is one comment
Increasingly vibe-coded codebase
“which has been great but is increasingly vibe-coded”
Comment from 23 Mar 2026 in “Dune3d: A parametric 3D CAD application” “has been great but is increasingly vibe-coded”
Comment from 24 Mar 2026 in “Dune3d: A parametric 3D CAD application” Documentation is lacking
“it's always 0. Lots of other issues/bugs too, and severely lacking in ddocumentation.”
Comment from 21 Dec 2025 in “OpenSCAD is kinda neat” “it has a lot of issues, mainly in documentation”
Comment from 24 Mar 2026 in “Dune3d: A parametric 3D CAD application” Needs lots of code
“Build123d seems to require a lot of coding to calculate constraints and positions”
Comment from 11 Oct 2026 in “OpenSCAD the Programmers Solid 3D CAD Modeller” “I haven't found it as ergonomic as SolidPython”
Comment from 19 Oct 2026 in “RepRapMicron”
Other code-based CAD libraries people recommend
The three most recommended other code-based CAD libraries, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| build123dThis page | 53 | 9 | 85% | 11 | 1 yr3 owners | Approved |
| CadQuery | 40 | 6 | 87% | 12 | — | Approved |
| BOSL2 library for OpenSCAD | 22 | 3 | 88% | 8 | — | Approved |
| Cadova | 5 | 0 | 100% | 2 | — | — |
What people said
40 of the 78 comments that mention it, newest first. Each links to the original comment.
“I model with `build123d` or `openscad` using Claude Code to do the heavy lifting”
“I haven't found it as ergonomic as SolidPython”
“they don't even bother looking for true programmatic CAD like build123d”
“I have found better results with `build123d` than with OpenSCAD”
“build123d was better suited to technical drawings”
“Build123d seems to require a lot of coding to calculate constraints and positions”
“something built on the open-source Open Cascade geometry kernel”
“I have been using these models to make 3d models with build123d — they are great at it.”
“It can do build123d too brother, and generate step files.”
“I've tried Sol on build123d and it was completely unusable”
“I like build123d simply because it can export proper STEP (like CadQuery) but has a nicely python friendly design.”
“I use build123d with Python and the results are pretty good!”
“I've had a positive experience building a library of parametric HVAC duct parts using Claude, Gemini and Codex”
“the recent progress of FreeCAD and its spin-off libraries cadquery and build123d will be better to push”
“Recently I've been using Claude Code with build123d and it's pretty good”
“It was a great experience and wouldn't generally be easy to do with Fusion 360.”
“I just got started with build123d which is great”
“Ok here is my result, which matches up well with the examples I have found from McMaster Carr.”
“seems like an LLM should have no problem writing python code”
“Something I haven't seen before is their filter syntax for disambiguating solutions.”
“Build123d is much better (supports STEP export and import)”
“It's really useful to get an iteration loop going with an LLM.”
“it seems to solve all of my gripes with OpenSCAD”
“It is not my main CAD software (build123d is), but I really appreciate the workflow.”
“it has a lot of issues, mainly in documentation”
“has been great but is increasingly vibe-coded”
“which has been great but is increasingly vibe-coded”
“go straight for build123d which operates on real solid models (BREP)”
“I'm playing with this now too and it's really wonderful”
“I've enjoyed Build123d (and it's over-loaded python operators) as an alternative to OpenSCAD”
“I think it is much more capable than OpenSCAD due to BREP and Python.”
“Build123d can do chamfers. You can also do relative positioning by selecting positions from the first shape.”
“Its a Python library with an active and accessible community.”
“you can use CadQuery/Build123D and generate STEP files for some of it”
“it's always 0. Lots of other issues/bugs too, and severely lacking in ddocumentation.”
“they all have facilities to operate on generated geometry such as edges, faces and vertices”
“I really recommend you look at CadQuery/Build123D”
“worth also looking at cadquery, build123d and similar”
“This growing CAD library is quickly gaining attention in the Python and parametric modeling communities.”
“at least build123d (which I had never heard of, thanks!) can export STEP”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.