Read How to Repair an STL File for 3D Printing, How to Make an STL File Printable, check non-manifold geometry, or check for open edges.
Inspect and clean STL files
STL Repair Tool
Find disconnected pieces and choose which to keep. You can also clean duplicate or degenerate triangles and simple orientation issues.
Choose an STL file
Choosing a file finds separate pieces in your browser. All pieces start kept; review them before downloading a changed copy. This step does not upload your file.
Pieces are joined only when triangles share a complete edge with exactly matching coordinates. Point contact, overlap or a small gap does not join them, and this mesh connectivity check does not identify slicer support regions or decide which parts the design needs.
Select a non-empty .stl file, up to 25 MiB.
Generated test geometry; choosing another file replaces it.
Try an example
Can I review disconnected pieces and download only the chosen body?
Settings: On STL Repair, choose the generated example to open review automatically, press Keep largest part, inspect the reversible selection, then download the STL with kept pieces. Millimetres are assumed, not stored in STL.
Downloads this public control, then opens it locally. Your own file can still be chosen above.
Read the explanation · Download and compare controls · Methods and processing
Need standard STL cleanup instead?
Clean duplicate and degenerate triangles and correct simple orientation issues. Pressing the button uploads the selected file to InspectMesh for server processing. Keep an original copy. It cannot reliably fill holes or repair every non-manifold model.
How disconnected-piece review works and its limits
Review loose parts in three steps
- Choose one STL above. Automatic detection retains every piece.
- The example opens review automatically. Use Previous and Next to inspect pieces, or press Keep largest part to propose the greatest-area component. Similar areas trigger a warning and require confirmation. Restore intended pieces with Keep, or reset to keep all.
- Download STL with kept pieces to save the retained triangles, then inspect the separate copy in your slicer.
Download the binary demonstration STL or the ASCII version. These are generated files for testing through the picker above.
Counterexample: separate pieces can be intentional
Two intended cube parts has 20-unit and 19-unit cubes: 2 parts / 24 triangles. Both start retained. Their areas differ by less than 10%, so Keep largest part first warns and asks for confirmation. Reset restores both. Removing the smaller one by size alone would discard an intended object. Lettering, inner cavity surfaces and print-in-place mechanisms can also contain necessary disconnected shells.
What does a piece finding establish?
The connectivity method is described beside file selection above. Component counts do not establish defects or design intent. Open and non-manifold pieces have area and bounds, but no inferred reliable volume. Zero-area faces require an explicit standard repair first.
Can size identify unwanted pieces?
No. The review order uses surface area, with triangle count and stable part ID as tie-breakers. Smaller islands or loose parts may be important. Inspect each piece in context before changing its Keep selection.
Do dimensions change?
Retained vertices keep their coordinates, winding, scale and position. Overall file bounds can shrink when you remove an outer piece; the retained body is not resized or moved. STL is unitless; displayed millimetres are assumed. ASCII coordinates are retained in ASCII output; binary input keeps its stored Float32 coordinates. Normals are recalculated, and colour/material metadata is not preserved.
What about floating regions in a slicer's layer preview?
A slicer floating region can belong to one continuous model. This tool does not detect every unsupported region or generate supports. Removing disconnected pieces does not guarantee printability, manifoldness or watertightness. Use the disconnected-shell guide and STL Print Preflight to interpret remaining issues.
Component analysis is limited to the existing 25 MiB file allowance and 500,000 triangles. Heavy parsing, connectivity and verified export run in a cancellable browser worker. The list shows 30 parts per page, and the full-resolution preview batches retained and removed triangles into two meshes. No unlimited-file promise is made.
Local part removal and explicit server cleanup
Choose a repair and protect intentional openings
The owned cube plus an exact duplicate triangle has 13 faces. Removing that duplicate should restore 12 without inventing a surface. A missing whole cube face is a different problem: cleanup cannot recreate its intended design.
Interpret the result and choose the next step
Standard STL cleanup explicitly uploads your selected file, up to the current 25 MiB guest limit, for server processing. Disconnected-piece detection and selection-only export run locally and never silently combine with that action. STL has no declared unit. Review the actual removal counts and skipped reasons, download the separate copy, then reselect it for preflight and revision comparison. No unconditional printability claim is made.
Compare input and cleaned STL surfacesCleanup removes redundant faces, not missing design
The supported actions remove exact duplicate triangles and degenerate triangles (faces with no useful area), then attempt orientation correction in closed manifold regions. Retained vertex coordinates are not smoothed or resized. Removing a redundant face is different from reconstructing a missing surface: holes, intersecting bodies and ambiguous internal geometry need a design decision in CAD.
Try a narrow, reproducible repair
Download the 20 mm cube with one duplicate triangle. It contains 13 triangles: the 12 faces of a consistently oriented cube and one repeated triangle. Select it above, then explicitly submit cleanup. Check that the report removes one duplicate, preserves 20 × 20 × 20 coordinate spans and produces a separate copy. Reopen that copy, inspect the six surfaces, check topology and compare it with the original. A smaller triangle count alone does not prove that intended features survived.
Before submitting and after downloading
The retained local processor run removed the duplicate and reopened its actual saved output as a valid 12-triangle cube with 20-unit spans. Download that saved cleanup control and its reopened report. This is evidence for that narrow operation, not a claim that every defective STL can be repaired or that production is running this revision.
STL cleanup uploads the selected file to InspectMesh for server processing when you press Clean STL safely. Selecting or downloading an example is not permission to upload it automatically. Keep your original and avoid submitting confidential designs unless this processing is appropriate for you.
Malformed records, invalid coordinates or upload-limit failures can prevent a job from running. A completed job can also report that no safe change is available. Read skipped reasons instead of repeatedly submitting the same file. If open boundaries remain, return to the source model or an explicit mesh-editing workflow; this tool cannot infer the missing shape.
Stop using the cleaned derivative if dimensions, intended shells or important features change unexpectedly. The output passing mesh validation still does not certify strength, fit or a physical print. Compare the revised surfaces before accepting it.
Review the saved revision
After local piece selection or explicit server cleanup, download the changed copy and retain the original. Reopen the exact saved bytes in the STL viewer, inspect every intended kept component and verify dimensions. Compare the files in original coordinates under the same intended unit assumption when design fidelity matters.
Review intended changes and named features before replacing a workflow input. Cleanup does not reconstruct a missing opening, establish design intent or perform a Boolean union.