CADProps Specifications: Data Handling, Limits and Formats

Data security and retention

• Where files are processed. CAD files are processed on CADProps servers. Your browser receives a display mesh and the calculated properties.
• Encryption in transit. All pages and API requests use HTTPS with TLS 1.2 or TLS 1.3. HTTP Strict Transport Security is enabled.
• Guest uploads. A guest file is deleted from the server about one hour after upload; the workspace shows the exact retention period. The original file, its preview and its calculated results are all removed. Clear removes the workspace copy straight away.
• Signed-in uploads. These are saved to your account library on purpose. They expire 90 days after you last use them, and deleting one removes its copy and results and revokes its share links.
• Share links. A link shows a fixed snapshot of one model for the 7 or 30 days you choose. Recipients cannot download the original CAD file.
• No outside processing. Original CAD files are not sent to external CAD processing services. Uploaded files, model data and measurement results are not used to train AI models.

The privacy policy has the full statement, including cookies, analytics and who can access stored files.

Processing architecture

• Exact geometry. STEP and IGES B-Rep geometry is read with Open CASCADE Technology (OCCT) 7.9. For STEP files, assembly structure, names and colours are kept. Bounding boxes, surface area and closed-solid volume are calculated from the exact geometry rather than from the display mesh.
• Performance-critical steps. Mesh orientation repair and STEP integrity checks run in C++.
• Native formats. SolidWorks, Inventor, NX, CATIA, Parasolid, ACIS and JT files are converted in an isolated container that has no internet access.
• 2D drawings. DWG drawings are read with LibreDWG.
• Sandboxing. Each file is processed in a sandboxed worker with its own memory, CPU-time and output limits.
• Browser display. The viewer renders with three.js over WebGL 2. Display meshes are decoded in a Web Worker so the page stays responsive.

Supported formats

• Open directly: STEP/STP, IGES/IGS, STL, OBJ, 3MF, static GLB/glTF, DWG, DXF, and ZIP packages that hold an assembly with its references.
• Through native conversion: SolidWorks SLDPRT/SLDASM, Autodesk Inventor IPT/IAM, Siemens NX PRT, CATIA CATPart/CATProduct, Parasolid X_T, ACIS SAT, and JT with readable solids.
• STEP files are recognised by their ISO 10303-21 header. AP203, AP214 and AP242 exports with B-Rep geometry go through the same reader. The mesh-only STEP export writes an AP242 file of triangles, not exact solids.

Version and geometry details for each format are listed under supported formats and limitations.

File size and assembly limits

Over these limits, a file is rejected with an explanation. Exports with thousands of loose bodies are grouped into combined parts instead, and assemblies with missing components are marked as incomplete. For larger models, use desktop CAD software or ask about a custom private deployment.

Measured load times

Measured on the production service on 2026-10-06.

• Production sample. Across 60 file previews, the median time to a finished preview was 3.4 seconds and 91.7% finished within 10 seconds.
• Public test assembly. A 50 MB public Raspberry Pi 4B STEP assembly, which includes a part of 144,623 mesh faces, took about 35 seconds on the production server.
• Small parts. In development benchmarks, STEP parts of 0.01–1.2 MB showed their first frame in about 1.3–2.4 seconds (95th percentile).

Viewer and measurement functions

• Measurement: point coordinates, point-to-point distance, edge length, circle diameter and radius, face-to-face distance, angle, surface area and volume. Metric and imperial units are both available.
• Model properties: bounding box (length × width × height), surface area, volume, and mass from a density you enter.
• Assembly tools: assembly tree with per-part visibility, one movable X/Y/Z section plane with closed caps, and an exploded view.
• Export and comparison: CSV export of properties for one or many files, PNG image export, and STEP solid comparison that reports removed, added and common volume.
• Mobile: the viewer works in mobile browsers, with a responsive layout and touch controls.

See how calculations work for the assumptions behind each value.

Best fit

• Machining and quoting staff checking a customer's STEP file for size, volume and estimated weight before a quote.
• Purchasing and supply-chain engineers confirming part dimensions or assembly contents without a CAD licence.
• Incoming inspection and quality staff comparing a received model against its previous revision.
• Anyone on a phone or a locked-down PC who needs to look at a CAD file without installing software.

Original article: CADProps · https://www.cadprops.com/specifications/