Who runs this

Why it exists

I design telescopes in Fusion 360 and print them. That means a steady traffic of STEP, STL and 3MF files between CAD, slicers and machine shops, and a steady supply of the questions this site answers: what a format actually stores, why a part came in 25.4 times too small, and what a conversion silently threw away. The free converters I found either uploaded the file to a server they said nothing about, or reported success without saying what was lost. This site is the tool I wanted.

What is checked, and how

The site's claims are generated from evidence rather than written by hand, and the rules are enforced in code, not in a style guide.

• A conversion gets a page only after it passes a test. Every one of the 120 pair pages is generated from a run against a public test corpus. A pair that fails gets no page. The corpus is CC0 and every file in it carries its provenance.
• Every fact carries its source and the date it was checked. The capability table on each format page links to the standard, the vendor's documentation or the maintainer's source, and shows when it was read. Where a source could not confirm something, the row says "unconfirmed" rather than guessing.
• Browser tools keep your CAD file local. The registry lists 105 browser conversion pairs and one hosted STL-to-STEP route. The other 14 STEP pairs are core-only references with no public upload route. Hosted conversion uploads the selected file when the service is available. Its download link expires one hour after the job is queued; storage cleanup runs separately, so a stored copy can outlast its link. The job schema stores no IP address, filename, account or CAD contents. Separate rate-limit records and Cloudflare Turnstile handle upload abuse prevention. The privacy page explains these records, bot verification and analytics.
• Every component we ship is listed. The licences page names each library, its licence, the exact artefact served and its hash, so the build can be reproduced. This build: occt 0.0.23-4gb, three 0.185.1, rhino3dm 8.32.2, built 2026-10-01.

Scope and limits

The 3D conversion tools do not read DWG, DXF, SolidWorks or Parasolid files. Separate drawing tools accept supported DXF and SVG inputs when enabled. A missing reader or writer is a limit of this implementation, not a claim that no other browser tool can support that format. STL-to-STEP produces planar faces from mesh triangles; it cannot recover curved CAD surfaces or native design history.

Enabled file-preparation tools list their supported checks and operations. They do not perform general surface reconstruction, fill holes or establish manufacturing suitability. A refused operation or an unresolved defect remains visible.

Corrections

If a fact on a format page is wrong, or a conversion did something its page does not describe, write to jeff@hooton.codes with the page and, if you can share it, the file. Corrections are made to the source table, with the new source and date, so the fix shows on the page with its evidence.