Degenerate triangles
RemovedFaces with overlapping or nearly collinear points and almost no usable area are excluded from the output.
STL REPAIR & MESH CHECKER
Clean Your STL Mesh Before 3D Printing
Upload an STL, remove degenerate triangles, and check how many mesh edges still need inspection. Review the cleanup counts and download a cleaned file for your next step.
Remove degenerate trianglesCheck problematic edgesReview cleanup countsDownload cleaned STL
STL files up to 50 MB · Local browser processing · Further repair may still be needed
STL Mesh Cleanup
Your STL is processed locally in your browser.
A qualifying paid account with a positive credit balance is required. Local cleanup does not deduct additional credits.
Mesh Diagnostics
Upload an STL to see cleanup results here.
Degenerate triangles removed
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Edges requiring further inspection
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Triangle count shows faces removed by cleanup. Edge count indicates connectivity issues for further inspection; it is not the number of holes. Additional mesh validation may be needed before printing.
THREE SIMPLE STEPS
Check and clean an STL file online
Run a first cleanup pass without rebuilding your model. The tool removes degenerate or invalid triangle faces, recalculates normals for surviving triangles, and counts edges whose connectivity differs from the expected two-face relationship.
It does not automatically close holes, join disconnected shells, or make every STL watertight.
From upload to diagnostics
01
Upload an STL file up to 50 MB.
02
Clean invalid triangles and recalculate normals in your browser.
03
Review both counts and download the cleaned STL for further checks.
UNDERSTAND THE CLEANUP
Some STL errors can be cleaned; others need more work
This tool performs a limited cleanup and reports a mesh connectivity count. It does not reconstruct missing geometry or resolve every topology problem.
Invalid coordinate values
FilteredTriangles containing non-finite coordinates can be discarded. This does not guarantee detection of every malformed or corrupted file.
Mesh normals
RecalculatedNormals are recalculated for surviving triangle geometry. Reversed faces and inconsistent winding are not all automatically corrected.
Problematic edges
CountedThe tool counts edges that are not shared by exactly two triangles. The count may include open boundaries or over-shared edges.
Holes in the mesh
Not filledOpen boundaries may remain after cleanup. Use a dedicated repair tool if you need holes closed.
Self-intersections and shells
Not repairedThe tool does not resolve intersecting surfaces, merge separate shells, or connect floating components.
KNOW WHAT THE NUMBERS MEAN
Read your STL cleanup report
The result panel shows two diagnostic counts from the cleanup operation. They describe specific checks and do not certify the complete model.
Degenerate triangles removed
This is the number of invalid or near-zero-area triangles excluded from the output. Zero means this check removed none; it does not prove the original mesh had no other issues.
Edges requiring further inspection
This counts edges that do not have exactly two adjacent triangles under the tool's connectivity check. It is not a count of holes and does not locate every defect.
Even a zero edge count does not certify watertightness or printability. Self-intersections, disconnected parts, orientation, and wall thickness may need separate checks.
COMMON STL CLEANUP SCENARIOS
Give an STL a first cleanup pass
Different files can have different mesh issues. These are common situations where a first cleanup and diagnostic count may help; no before-and-after sample is presented as a verified result.
A figurine before slicing
Remove detected invalid faces and review edge diagnostics before preparing a collectible or small model in your slicer.
Cleanup counts · Further slicer checks
A downloaded 3D model
Run a cleanup pass on an STL from a model library and use the counts to decide whether it needs more attention.
First-pass mesh inspection
A photo-based relief STL
Check an exported lithophane or other relief STL before opening it in your slicer. Confirm the intended geometry remains after cleanup.
Cleaned STL · Inspect before printing
These are usage examples, not fabricated tool output. The workspace displays only counts from the STL you process.
UNDERSTAND MESH CONNECTIVITY
Why some edges need further inspection
On a conventional closed triangle surface, an edge is commonly shared by two triangles. Edges with a different relationship may indicate an open boundary or another connectivity issue.
An edge used by one triangle can indicate an open boundary. An edge used by more than two triangles can indicate a non-manifold connection.
The report gives a total count only. It does not identify each edge location or equate the count with the number of holes.
AFTER THE CLEANUP
Check your model before printing
A cleaned STL is not automatically a printable STL. Validate the output in your slicer or mesh editor.
- •Mesh integrity: check for open boundaries and other defects.
- •Dimensions: verify scale and units in your target software.
- •Wall thickness: check thin features against your printer and material.
- •Slicer preview: inspect toolpaths for gaps or missing surfaces.
This tool does not guarantee a successful print or correct every mesh defect.
COMMON SITUATIONS
When to check an STL mesh
Before 3D printing
Run a preliminary cleanup, then validate the output in the slicer you plan to use.
After downloading a model
Inspect an STL from a file library before spending time and material on a print.
After converting to STL
Check a converted model for invalid faces and edge connectivity issues.
After editing a mesh
Modeling and mesh operations can introduce unexpected geometry; review the cleanup counts.
Before sharing a model
Use the cleanup as one preliminary check, and disclose any remaining issues you find.
When a slicer reports an issue
This tool may remove degenerate faces. Other warnings can require a more complete repair application.
A FIRST PASS
STL cleanup and diagnostics
Removes detected degenerate faces, recalculates normals, counts edges that need inspection, and exports a cleaned STL for additional checks.
FOR COMPLEX MESH PROBLEMS
When you need full mesh repair
Hole filling, shell merging, self-intersection repair, surface reconstruction, and topology rebuilding are outside this tool's current capabilities. Use a dedicated mesh editor for those operations.
SIMPLE LOCAL PROCESSING
Clean your STL in your browser
The browser reads and processes the STL locally. It does not send the model to an AI generation service or attempt to redesign the object.
Local browser processingNo AI regenerationClear cleanup countsDownloadable cleaned STL
Access requires a qualifying paid account with a positive credit balance. Local processing does not deduct additional credits.
Continue with related 3D tools
Image to Lithophane
Create a thickness-based photo relief STL and prepare it for printing.
Explore tool →Photo to STLExplore an estimated 3D model from a picture and export STL.
Explore tool →Image to 3DCreate a 3D asset from a reference image.
Explore tool →AI 3D RetopologyExplore a different polygon layout for a 3D model.
Explore tool →BEFORE YOU CLEAN
Frequently asked questions
How can I repair an STL file online?+
Upload a compatible STL and start cleanup. The tool removes degenerate triangles, recalculates normals, and checks edge connectivity. Review the counts and download the cleaned STL for further inspection.
What STL problems can this tool fix?+
It removes degenerate or invalid triangles detected by its cleanup checks and recalculates normals. Other issues, including holes and non-manifold connections, may be reported but are not automatically corrected.
Can it fix non-manifold STL geometry?+
Not automatically. It counts edges that do not have exactly two adjacent triangles, but it does not reconstruct the mesh to repair those connections.
Does this STL repair tool fill holes?+
No. It does not automatically fill missing surfaces or close open boundaries. A dedicated mesh repair application may be needed.
Can it make my STL watertight?+
The cleaned file may still have open boundaries or other geometry problems. This tool does not guarantee a watertight result or replace validation before printing.
What is a degenerate triangle?+
It is a triangle with almost no surface area, often because its points overlap or lie on a straight line. Such faces can be removed during cleanup.
Does the tool remove degenerate faces automatically?+
Yes. It checks triangle data and excludes faces that meet its invalid or near-zero-area criteria. The report shows how many were removed.
What does Edges Requiring Further Inspection mean?+
It counts edges that do not have exactly two adjacent triangles in this connectivity check. These can include open boundaries or edges shared by too many faces; the count is not the number of holes.
If the problem-edge count is zero, is my STL printable?+
Not necessarily. This check may find no flagged edges while self-intersections, disconnected parts, orientation issues, or unsuitable wall thickness remain.
Can this tool repair inverted normals?+
It recalculates normals for surviving geometry but does not guarantee correction of every reversed face or inconsistent triangle winding.
Does it repair self-intersecting meshes?+
No. It does not detect and resolve all surface intersections. Those models may need a more advanced geometry repair workflow.
Can it connect disconnected mesh parts?+
No. It does not merge separate shells or join disconnected components into one solid object.
Will it change the shape of my 3D model?+
It does not intentionally remodel the object, but it removes detected invalid triangles. Inspect the output to confirm the intended geometry is preserved.
Does it reduce the polygon count?+
It can reduce the triangle count by removing invalid faces, but it does not perform general decimation, remeshing, or mesh simplification.
What file formats does it support?+
The tool accepts STL files and exports a cleaned STL. It does not directly accept OBJ, FBX, GLB, or other model formats.
What is the maximum upload size?+
Compatible STL files can be up to 50 MB. Large or complex files may need more browser memory and processing time.
Does it support binary and ASCII STL?+
The underlying parser handles common binary and ASCII STL representations. Malformed or unsupported files can still fail to load, and successful parsing does not certify valid geometry.
Can I use it before 3D printing?+
Yes, as a preliminary cleanup and diagnostic step. Check the output in your slicer, including dimensions, wall thickness, mesh integrity, and print settings.
Can I use it with Cura or PrusaSlicer?+
Download the cleaned STL and open it in compatible slicers such as Cura or PrusaSlicer. They may perform their own checks and report additional issues.
Can I preview the repaired STL in 3D?+
The current workspace shows cleanup counts and provides a downloadable STL. It does not include an interactive before-and-after viewer; inspect the file in compatible 3D software.
Will the STL dimensions stay the same?+
The tool does not intentionally rescale the remaining geometry. STL files do not reliably identify physical units, so verify dimensions in your target software.
What if no degenerate triangles are found?+
The tool can remove zero triangles and still provide a result. That does not prove the file has no other mesh problems; review the edge count and inspect the output.
What if all triangles are invalid?+
If no valid triangles remain, the tool cannot export a meaningful cleaned model and returns an error instead of an empty STL.
Does this tool use AI?+
No. It uses local geometry processing to clean and inspect triangle data. It does not run AI inference or generate missing parts.
Is the STL repair tool free?+
Local cleanup does not deduct additional credits, but access requires a qualifying paid Create3DOnline account with a positive credit balance.
Is my STL uploaded to a server?+
The mesh cleanup runs locally in your browser. The selected STL is not uploaded to a remote AI service for processing. Account authorization is checked separately.
Can I use it on Mac and Windows?+
It is designed for compatible modern browsers. Performance depends on your device and the complexity of the STL file.
Can I use the cleaned STL commercially?+
Use the output subject to your rights to the original model and its license terms. The cleanup does not grant ownership or commercial rights to third-party designs.
CHECK YOUR STL BEFORE YOUR NEXT PRINT
A better print starts with a closer look at your STL
Clean detected invalid triangles, review whether edges need further inspection, then validate the file in your slicer before printing.
Start STL cleanupSTL upload · Triangle cleanup · Edge diagnostics · Cleaned STL download