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Windows 10 & Windows 11 Updated 2026-10-15

Repair a broken STL or 3MF and see every change, on this PC.

MeshMedic is a Windows app from Automata Labs that repairs holes, non-manifold edges, and inverted triangles in STL, OBJ, and 3MF files, and shows you what changed before you export. Check the Before and After counts, see every repaired triangle in blue in a 3D preview, and write a new file in the same format, with a 3MF’s colors, materials, and components kept. The original is never overwritten.

One-time purchase · 15-day free trial in the Microsoft Store · One-time purchase. No subscriptions. Local-first.
Pay once. Own it forever.

One-time purchase on the Microsoft Store · No subscription · Instant install

Get it from Microsoft

Buy through the Microsoft Store—instant install, automatic updates, and a Microsoft receipt for easy expensing. No account needed on our site, and no subscription on Store purchases.

How it works See the screens

stl, obj, 3mf · before and after counts · 3d preview · 3mf colors kept · originals never overwritten · nothing uploads

MeshMedic defect table and repair preview

MeshMedic after repairing bracket.stl: the defect table shows Inverted triangles 4 to 0 and Holes 2 to 0, both Fixed, and the 3D preview draws the repaired triangles in blue.
Repair, then check. The table shows each defect before and after, and the preview paints every changed triangle blue.

The problem

The job is due tonight, and the slicer flags the mesh.

A downloaded model, a CAD export, or a customer’s file arrives with holes, triangles facing inward, or edges shared by too many faces. The slicer warns, drops a wall, or fills a gap it should leave open. Rebuilding the model takes hours you do not have, a full modeling suite is a lot to learn for one fix, and an upload site wants the file on its server.

With MeshMedic

Open the file. Repair. Check. Export.

MeshMedic counts each defect for every part, repairs them in one step, and draws every triangle it flipped or added in blue, with Show before to compare. When the After column reads right, Export writes a new STL, OBJ, or 3MF in the same format and shows a short note of what changed. The original is only read.

Key benefits

Find the defects, fix them, and see the fix first

Every defect counted, part by part

Open an STL, OBJ, or 3MF and MeshMedic lists non-manifold edges, inverted triangles, and holes for every part in a table with Before, After, and Status columns, plus a row for degenerate and duplicate triangles when the file has any. Each part is labeled by name, an object used twice shows ×2, and a clean file says No defects found.

One repair pass

Repair welds coincident vertices, removes zero-area and duplicate triangles, splits non-manifold edges and bow-tie vertices, orients every shell outward, and caps holes with triangles that face the right way.

Every change shown in 3D

Triangles the repair flipped or added turn blue. Show before switches back to the mesh as it was, with inverted triangles in red. Orbit with the mouse or the arrow keys, and zoom with the wheel.

3MF projects kept intact

Colors, materials, components, build items, metadata, and the thumbnail come through as they were. Only the vertices and triangles of the repaired objects are rewritten.

A before and after note

After each export, a short note lists the counts before and after for every part and the triangles flipped, added, and removed. Copy it, or save it as a .txt file for the job.

A new file, every time

Export writes the same format under a new name, with -repaired suggested. Saving over the original is refused, even through a junction, a hard link, or a network path.

How it works

Open, check, repair, export

Open

Choose Open file and pick an STL, OBJ, or 3MF, or pick one from the Recent list. MeshMedic reads it, shows the name, format, parts, and triangle count, and fills in the Before column.

Check

Read the counts for non-manifold edges, inverted triangles, and holes, and look at the preview, where inverted triangles show in red. A clean file says No defects found and is ready as it is.

Repair

Choose Repair. The After column and the Status fill in, every triangle the repair flipped or added turns blue, and Show before lets you compare the two meshes.

Export

Choose Export and name the new file in the Windows save dialog. MeshMedic writes the same format it opened and shows the before and after note, ready to copy or save.

Every export is a new file, so you can repair the same original as often as you like.

See it in action

The defects, the repair, and the new file

MeshMedic with bracket.stl open: the defect table lists Non-manifold edges 0, Inverted triangles 4, and Holes 2, and the 3D preview marks the inverted triangles in red.
Open a file and see what is wrong. Each defect is counted for every part, and inverted triangles show in red.
MeshMedic after Repair: Inverted triangles and Holes both read 0 and Fixed, and the repaired triangles of the bracket are drawn in blue.
Repair, then compare. Changed triangles turn blue, and Show before brings back the mesh as it was.
The Windows Save As dialog over MeshMedic with the suggested name phone-stand-repaired.3mf and the type 3MF file.
Export to a new file. The suggested name ends in -repaired, and the format matches the original.
MeshMedic after exporting phone-stand-repaired.3mf: the note lists 4 inverted triangles and 1 hole before and none after, with 4 triangles flipped and 2 added, and Copy, Save note, and Close buttons.
Done. The note records the counts before and after and every flipped and added triangle, ready to copy or save.

Screenshots show sample parts made for testing.

Privacy

Nothing uploads

MeshMedic runs on your PC in the Windows app sandbox and declares no capabilities. It makes no network connections, has no account, and collects no telemetry. It reads only the files you pick in the Windows open dialog, writes only the files you name in the save dialog, and keeps its Recent list on this PC. Your original files are never overwritten.

What you get

  • Opens STL (binary and ASCII), OBJ, and 3MF files you pick.
  • A defect table with Before, After, and Status for every part.
  • One-step repair: weld, split non-manifold edges, flip inverted triangles, and cap holes.
  • A 3D preview with repaired triangles in blue and a Show before toggle.
  • Export in the same format, with the original name plus -repaired suggested.
  • 3MF colors, materials, components, and build items carried through.
  • A before and after note to copy or save as a .txt file.
  • A Recent list that reopens your last 25 files without the open dialog.

Try it on the file that gave you trouble.

The Microsoft Store runs a 15-day free trial with every feature. Open the STL or 3MF your slicer flagged, repair it, and compare the before and after counts and the preview. If it fits your work, buy it once. There is no subscription.

Pay once. Own it forever.

One-time purchase on the Microsoft Store · No subscription · Instant install

Get it from Microsoft

Buy through the Microsoft Store—instant install, automatic updates, and a Microsoft receipt for easy expensing. No account needed on our site, and no subscription on Store purchases.

Who uses it

  • Makers whose downloaded or exported STL shows errors in the slicer and who need a repaired copy tonight
  • Print shops and print farms checking customer STL, OBJ, and 3MF files at intake and keeping a note of every repair
  • Designers who need a multi-color or multi-part 3MF repaired with its colors, materials, and components kept
  • Engineers and teams whose client models have to stay on the PC, with no upload to an online repair service

FAQ

Quick answers about MeshMedic

What is MeshMedic?

MeshMedic is a Windows app that repairs a broken STL, OBJ, or 3MF file and shows you what changed before you export. It counts non-manifold edges, inverted triangles, and holes, repairs them in one step, draws every changed triangle in blue in a 3D preview, and writes a new file with a short before and after note. The original is never overwritten, and nothing uploads.

How do I repair a file with it?

Choose Open file and pick an STL, OBJ, or 3MF. Read the Before column in the table, then choose Repair. Check the After column and the blue triangles in the preview, and use Show before to compare. Choose Export and save a new file; MeshMedic suggests the original name with -repaired added, and the note appears as soon as the file is written.

Which defects does it find and fix?

Non-manifold edges, where three or more triangles share an edge; inverted triangles, which face the wrong way; and holes, which are loops of open edges. It also removes zero-area and duplicate triangles, welds coincident vertices, splits bow-tie vertices, and clears stray fragments too small to enclose a volume. Each defect gets a row with Before, After, and Status.

Which file formats does it open and export?

MeshMedic opens STL (binary and ASCII), OBJ, and 3MF, and exports the same format it opened. A binary STL stays binary and an ASCII STL stays ASCII. An OBJ keeps its objects, groups, materials, and smoothing groups. A 3MF keeps its colors, materials, components, build items, metadata, and thumbnail, with only the repaired mesh changed.

Will a 3MF keep its colors and components?

Yes. MeshMedic copies every entry in the 3MF package byte for byte except the model parts that hold a repaired object, and inside those it replaces only the vertices and triangles. Each triangle keeps its color or material reference through the repair, components and build items come through as they were, and an object used twice is repaired once.

How do I see what the repair changed?

Three ways. The table shows each defect before and after, with a status such as Fixed. The 3D preview draws every triangle the repair flipped or added in blue, and Show before switches back to the mesh as it was, with inverted triangles in red. After the export, the note lists the counts and every change.

What is in the before and after note?

The source and export file names, then for every part the triangles, non-manifold edges, inverted triangles, and holes before and after the repair, and the changes: triangles flipped, added, and removed, and vertices welded and split. Copy puts the note on the clipboard, and Save note writes it as a .txt file to keep with the job.

What happens to my original file?

It stays exactly as it was. Every export is a new file you name in the Windows save dialog. MeshMedic refuses to save over the original, even through a shortcut folder (junction), a hard link, a network path, or after the original was renamed or moved. Because the whole file is read when you open it, the export works even if the original has moved since.

Does MeshMedic work offline?

Yes, fully. MeshMedic runs in the Windows app sandbox with no declared capabilities, makes no network connections, has no account, and collects no telemetry. It opens only the files you pick in the Windows open dialog and writes only the files you name in the save dialog, so customer and client models stay on your PC.

Can I reopen files I worked on earlier?

Yes. The Recent list in the left pane keeps your last 25 files with their format and folder. Click one to reopen it without the open dialog, even after a restart. If a file has since been moved or deleted, MeshMedic says so by name and takes it off the list.

What does it cost, and is there a trial?

MeshMedic is a one-time purchase in the Microsoft Store, and the listing shows the current price in your currency. The Store runs a 15-day free trial with every feature, and there is nothing to activate in the app. There is no subscription.

What Windows version do I need?

Windows 10 version 2004 or later, or Windows 11, on an x64 PC. A Direct3D 11 graphics card is recommended for the 3D preview, which falls back to software drawing without one. Plan on about 1 GB of available memory per million triangles; 8 GB of RAM covers meshes up to about 5 million triangles in binary STL, 3MF, or OBJ.

Still stuck? Email [email protected] after checking the Support Center.

Technical specifications

Technical specifications

Spec Implementation
Data Sovereignty Reads only the STL, OBJ, or 3MF files you pick in the Windows open dialog; writes only the repaired file and the optional .txt note you name in the save dialog, refusing to save over the original by any path; the Recent list stays in the app’s own storage on this PC
Telemetry Status None; no account, no telemetry, and no network client in the app
Core Runtime .NET 10 and WinUI 3 (Windows App SDK 2.5), packaged as MSIX and run in an AppContainer with no declared capabilities; repair engine and STL, OBJ, and 3MF readers and writers in managed C#; 3D preview drawn with Direct3D 11
Network Requirements Fully functional offline; the package declares no capabilities, including no internet access, and the app makes no network connections
Deployment Compatibility Windows 10 version 2004 or later and Windows 11, x64; one-time purchase on the Microsoft Store with a 15-day free trial
Inputs STL (binary and ASCII), OBJ, and 3MF, picked in the Windows open dialog or reopened from the Recent list of the last 25 files
Checks Non-manifold edges, inverted triangles, and holes for every part, plus degenerate and duplicate triangles; Before, After, and Status columns; No defects found for a clean file
Repair Welds coincident vertices, removes degenerate and duplicate triangles, splits non-manifold edges and bow-tie vertices, clears stray fragments, orients every shell outward, and caps holes
Preview 3D view with repaired and added triangles in blue, inverted triangles in red, and a Show before toggle; orbit and zoom with the mouse or the keyboard
Outputs A new file in the same format: STL in its original binary or ASCII flavor; OBJ with objects, groups, materials, and smoothing groups; 3MF with colors, materials, components, build items, metadata, and thumbnail kept; plus a before and after note to copy or save as .txt
System Direct3D 11 graphics recommended, with software drawing as a fallback; about 1 GB of available memory per million triangles, and 8 GB of RAM covers meshes up to about 5 million triangles in binary STL, 3MF, or OBJ

Guides by task

Pick the repair job in front of you

Broken STL files

Repair an STL file

Open the STL, choose Repair, check the blue patches and the Before and After counts, then export a new STL beside the original.

Non-manifold edges

Fix non-manifold STL

Open the file, read the Non-manifold edges row, choose Repair, and export once the After column reads 0 and the status says Fixed.

3MF projects

3MF repair

Open the 3MF, repair it, and export a new 3MF whose colors, materials, components, and build items match the original, with the repaired mesh in place.

Choosing a repair app

STL repair for Windows 11

A single-purpose Windows app for one job: open the mesh, repair it, check it, and export a new file, with nothing leaving your PC.

Pre-slice checks

Fix mesh errors before slicing

Make a repair pass part of intake: open the file, read the counts, repair, export the corrected copy, and file the note with the job.

Related Reading

Windows Tips & Tools

3MF vs STL for 3D Printing: What Each Format Keeps, and How to Repair Both

3MF vs STL, with OBJ alongside: what each format stores, why 3MF keeps colors and parts together, and how to repair each one and keep what it holds.

Workflow

How to Fix Flipped Normals in an STL File on Windows

How to fix flipped normals in an STL file on Windows: what inverted triangles are, how slicers react to them, and how to flip them back and export a new STL.

Deep Dive

Non-Manifold Edges, Holes, and Flipped Normals: STL Mesh Errors Explained

What non-manifold edges, holes, inverted triangles, and degenerate triangles are, why slicers stumble on them, and how each one is repaired.

A broken mesh in. A repaired file out.

MeshMedic counts the holes, non-manifold edges, and inverted triangles, repairs them in one step, shows every change in 3D, and writes a new STL, OBJ, or 3MF. The original is never overwritten, and nothing uploads.

One-time purchase. No subscriptions. Local-first.

Pay once. Own it forever.

One-time purchase on the Microsoft Store · No subscription · Instant install

Get it from Microsoft

Buy through the Microsoft Store—instant install, automatic updates, and a Microsoft receipt for easy expensing. No account needed on our site, and no subscription on Store purchases.

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