Your STL file never leaves your browser

An STL file, the standard 3D-model format a slicer turns into print instructions, contains your actual design. Uploading a proprietary or unreleased design to a mesh-checking tool is a real concern for anyone working on client work, a product before launch, or anything else they would rather not hand to a third-party server. PrintKinetic's mesh-inspection engines are built to make that concern unnecessary rather than to ask for trust: the analysis runs entirely inside your browser, using the file you select, and the file itself never becomes part of a network request. This guide explains what that actually means, what the local analysis can see, and what it honestly cannot validate.

The STL Manifold Readiness Check is the clearest example of how this works technically. When you select a binary STL file, the browser reads its bytes directly using a DataView-based parser, walks the triangle and edge data, and runs manifold and connected-component checks entirely in local memory. No fetch, upload, or background request carries the file, its geometry, or its filename anywhere. The check either happens in your browser or it does not happen at all; there is no server-side fallback quietly doing the work instead.

The Overhang and Bridge Risk Scan, Build Volume Fit Check, and Hole and Slot Printability Check all extend the same locally-parsed mesh data to different questions: which faces exceed a safe overhang angle, whether the model's bounding box fits the stated build volume, and whether hole and slot features meet nozzle-scale printability limits. Each of these reuses the same in-browser mesh parsing rather than sending the file anywhere new, so the privacy guarantee holds across every mesh-based engine on the site, not just the first one that reads the file.

It is just as important to be honest about what local mesh inspection cannot tell you. These checks see the geometry in the file: triangles, edges, watertightness, bounding dimensions. They cannot see your slicer's specific settings, your printer's calibration, your material's actual behavior, or anything about how the file was generated upstream in your CAD software. A model can pass every local geometry check and still print poorly because of a slicer setting or a machine issue the mesh itself gives no evidence of. Local inspection is a planning check on the model, not a print guarantee.

The same local-only principle applies to the file's metadata as well as its geometry. The filename, file size, and any embedded metadata in the STL stay in the browser along with the triangle data; none of it is logged, transmitted, or associated with any analytics event. Closing the tab or navigating away clears the file from memory, and reopening the page starts with nothing retained from the previous session.

Consider an independent designer working on a client's unreleased product, wary of running the file through any online STL checker after reading a service's terms and finding a broad license grant covering anything uploaded. Opening the browser's network inspector while using the STL Manifold Readiness Check and selecting the file shows exactly what the privacy claim implies: the mesh gets parsed, the manifold check runs, results render on screen, and the network panel shows no outgoing request carrying the file at any point. That is the same standard any sensitive design work should be checked against before trusting a tool with it, verified directly rather than taken on faith from a privacy statement alone.

The same local-processing approach also has real, honest limits worth stating rather than glossing over. Because the mesh never leaves the browser, PrintKinetic has no server-side record of which files were checked, which means there is also no way to recover a result if the tab is closed before it is copied or exported, and no aggregate usage data about the kinds of designs people are checking. That tradeoff, no convenience of saved history in exchange for a genuine privacy guarantee, is a deliberate one, and it is worth knowing before relying on the tool for a workflow that assumes results persist between sessions.

A common mistake is assuming a tool needs to explicitly promise privacy to be trustworthy, or conversely, that any browser-based tool is automatically private. Verify it yourself: a genuinely local tool works with your browser's network tools open and shows no outgoing request carrying the file. That is a testable claim, not a marketing one, and it is exactly the standard PrintKinetic's mesh-inspection engines are built to meet.

FAQ