Convert Rhino 4 to Rhino 3
Rhino 3 can't open .3dm files saved in Rhino 4 — the file format isn't forward-compatible, even one version back. RhinoFileConverter rewrites your file with the official OpenNURBS write pipeline (archive v40 → v30) so it opens natively in Rhino 3, with NURBS geometry, layers and blocks preserved.
Files will be converted to Rhino 3 (if compatible).
Why convert Rhino 4 files to Rhino 3?
You're modeling in Rhino 4 but need to hand the file to someone on Rhino 3 — a client, subcontractor, university lab, or team member who hasn't upgraded. Rhino 3 is still used by archived engineering files, and Rhino 4 is used by archived project files, older marine and jewelry workflows. Rather than asking them to upgrade or waiting for a re-export, convert the file here and send them a Rhino 3-native .3dm.
- Open Rhino 4 files in Rhino 3 without upgrading your license
- Official OpenNURBS 40 → 30 write pipeline
- NURBS surfaces, curves, meshes, layers and blocks preserved
- Runs in seconds, right in your browser — files stay private
- No plugins or software installation required
- Works on Windows, macOS and Linux
How it works
- 1
Upload your Rhino 4 .3dm file (drag & drop or browse)
- 2
We detect the file version instantly from the file header
- 3
Click Convert — the file is rewritten in Rhino 3 format using the official OpenNURBS libraries
- 4
The converted file downloads automatically
What actually changes between Rhino 4 and Rhino 3
Features introduced between Rhino 3 and Rhino 4 are downgraded to their closest Rhino 3 equivalent: clipping planes and refined history records.
The archive header is rewritten from OpenNURBS v40 (Rhino 4) to v30 (Rhino 3) so Rhino 3 recognises the file natively.
Because Rhino 3 is only one release behind Rhino 4, most objects survive without visible change. This is the cleanest possible downgrade.
Geometry preservation
NURBS surfaces, curves, meshes, layers, blocks and materials are preserved. clipping planes and refined history records are the ones that need translation: they get replaced with the closest Rhino 3-native representation (e.g. SubD → mesh or NURBS, newer annotations → base annotation types).
Tips for a clean Rhino 4 → Rhino 3 conversion
- Save a copy of the original Rhino 4 file before downgrading — some newer features can't be perfectly round-tripped back.
- If you're on Rhino 3 yourself and just want to hand the file to Rhino 3 colleagues, this is a one-click job.
- Rhino 3 predates modern annotation styles. Add dimensions and text after conversion in Rhino 3 rather than trying to preserve Rhino 4 styles.
Rhino 4 to Rhino 3 — FAQ
Can Rhino 3 open Rhino 4 files?
No. Rhino 3 uses OpenNURBS archive v30 and can't parse files saved with Rhino 4's newer v40 archive. Converting the file to the Rhino 3 format with RhinoFileConverter solves this in seconds.
What actually changes when I convert Rhino 4 to Rhino 3?
The archive version is rewritten from v40 to v30, and features that didn't exist yet in Rhino 3 — clipping planes and refined history records — are translated to their closest Rhino 3-native equivalent, exactly like Rhino's own "Save As Rhino 3".
Will my SubD or ShrinkWrap geometry survive from Rhino 4 to Rhino 3?
Rhino 3 predates SubD (added in Rhino 7). SubD objects are converted to a mesh or NURBS approximation on the way down. If you need editable NURBS geometry, run ToNURBS on SubDs in Rhino 4 before converting.
Is my file uploaded to a server?
No. The conversion runs entirely in your browser using the official OpenNURBS WebAssembly build. Your Rhino 4 model never leaves your computer.
Is there a file size limit?
Free conversions support .3dm files up to 25 MB. Paid plans raise the limit to 200 MB (single) and 250 MB (unlimited) — enough for most architecture and product-design files.