About this site
stepstl.com is a free converter that turns STEP and IGES CAD files into STL, and it does the whole job inside your browser tab. No account, no upload queue, no server that ever receives your geometry. Drop a file, pick a quality, download the STL with a measured bounding box and triangle count. The converter is a single page; this page, the privacy policy and the contact page are the only prose on the site.
Who runs it
This site is maintained by an independent developer. It is not a company, not a product line, and not a team: there is no support desk, no office and no legal entity behind it. The person who wrote the page is also the person who reads the mail at [email protected].
You do not have to tell us who you are to use the tool — nothing here asks for a name, an email address or a sign-up. In the same spirit, this page does not publish the developer’s name, address or company registration. “Maintained by an independent developer” is the whole description, and it is honest about the trade-off: you get a free tool that needs nothing from you, and you get a one-person site instead of an organisation with a service level.
Why it exists
Most online STEP→STL converters are upload services. You post a model that may still be under a client’s NDA to a server you know nothing about, receive a number back, and hope the file was deleted when you said it was. The reason this page exists is that the conversion never needed a server in the first place. OpenCASCADE — the modelling kernel CAD applications themselves are built on — compiles to WebAssembly, so the same kernel can run in a browser tab on your machine. Everything else here is the thin layer around it: the readers, three tessellation presets, an STL writer, and a plain canvas preview.
What it is built from
| Engine | occt-import-js 0.0.23, a WebAssembly build of OpenCASCADE Technology — 7,604,031 bytes of wasm, LGPL-2.1. |
|---|---|
| Code | Plain HTML, CSS and JavaScript with a dedicated worker. The STL serialisation, the statistics and the preview are this site’s own code. |
| Dependencies | None at runtime. No framework, no external fonts, no CDN, no build step in the browser. The only script that is not written here is the host’s cookieless visit counter, added by Cloudflare and named in the privacy policy. |
| Hosting | Static files served by Cloudflare Pages under the stepstl.com domain. There is no application server and no database. |
| Price | Free, with no sign-up and no usage limit. |
The licence texts ship with the page and are readable here: occt-import-js and OpenCASCADE (LGPL-2.1).
How it is paid for
The domain and the hosting come out of one person’s pocket. To cover them, this site may show third-party advertising — that is the only commercial thing about it, and what an ad does to your browser is described in the privacy policy. To be equally plain about the rest: no listing on this page is a paid placement, there are no affiliate links, no ranking or “featured” slot you can buy, and nothing you convert or merely look at is sold or handed to anyone. If advertising is live on a page, this section and the privacy policy will say who serves it.
Where the numbers come from
Every figure printed on the converter page — the 12 triangles and exactly 684 bytes of a plain 10 mm cube, the size of the wasm engine, each triangle count in the measurement table — was measured, not looked up. The engine version was run over the project’s own test files on the developer’s machine, then the same conversions were repeated in the browser, and the test scripts in the repository re-run every sample at all three presets and fail if a number on the page stops matching. So the numbers on the page have a referee you can run yourself: npm test.
The one figure that is never ours is the timing in the stats grid after a conversion: that is measured on your machine, which is the point of a tool that runs where the file already is.
What this tool will not do
- It will not repair a model. Gaps, self-intersections and open shells in the STEP file come out as the same holes in the STL. Fix the geometry in the CAD tool that made it.
- It will not move your part. Nothing is rotated, aligned, centred or re-scaled; orientation is your slicer’s job.
- It will not batch. One file per conversion, no folder drops, no queue.
- It will not remember anything. No history, no recent files, no account. Reload the page and you are at zero.
- It will not convert a file for you by email. There is no upload to do it with — describe the problem instead, and it can usually be diagnosed from the numbers the page already gave you.
Reporting a problem
Write to [email protected] — the contact page lists what makes a report answerable. Please do not attach a model you are not free to share: mail is not how this tool works, and a description with the file size, the quality preset and the bounding box the page reported is normally enough to find the cause.