What is the MTX file format?
A .mtx file is a Visual Studio Manual Test definition created by Microsoft's Team Test tooling, introduced with Visual Studio Team System in the mid-2000s. It stores an ordered list of test steps - plain-language instructions paired with expected results - that a human tester executes by hand inside Visual Studio's test runner, rather than any automated code.
The file is plain text or XML, encoded in UTF-8, and typically weighs only a few kilobytes. There is no binary magic signature; in XML variants the content opens with <?xml. A .mtx file lives inside a Visual Studio test project alongside related artifacts such as a .vsmdi test metadata file and a .trx results file.
Manual tests in .mtx format were designed for scenarios where automation was impractical - UI walkthroughs, exploratory testing, and compliance checklists - reflecting the workflow of Visual Studio Team System's built-in test runner.
The format is now considered legacy. Microsoft migrated manual testing first into Microsoft Test Manager (MTM) and subsequently into Azure DevOps Test Plans, where test cases are stored as work items rather than standalone files. Existing .mtx files remain viewable in any text editor.
Note: the .mtx extension is independently reused by unrelated applications - including Matlab matrix exports, The Sims body-shop files, and general math data formats - so context from the surrounding project is required to identify the actual type.
Security & safety
RISK: LOWA Visual Studio .mtx manual test is a text/XML definition with no executable payload, so it is low risk. The only caution is that, like any file in a downloaded code project, you should trust the source of the test solution it came from. If the .mtx is actually a matrix data file or game asset, it is similarly passive and low risk.
Format details
in a nutshell- Matrix data file (.mtx) - Text format storing a (often sparse) mathematical matrix, e.g. Matrix Market exchange files used in scientific computing.
- Maxis The Sims mesh/texture (.mtx) - Body/mesh data used by The Sims (Maxis) custom-content tools.
- Matlab-associated MTX data - Plain-text matrix data exchanged with Matlab/numerical tools.
Programs that open MTX files
Windows2 apps
Microsoft Visual Studio
Freemium Open the containing test project/solution in Visual Studio; the manual test opens in the test tooling (Community edition is free). 
Text editor (read-only inspection)
Open-source Open the .mtx in Notepad++/VS Code to read the test steps as text/XML, without the Visual Studio runner. Technical details
deep spec| File encoding | UTF-8 plain text or XML |
| Container format | XML-based text file using the Visual Studio Team Test schema |
| Magic bytes | No fixed binary signature; XML variants begin with <?xml (hex 3C 3F 78 6D 6C) |
| Typical file size | A few kilobytes - a short list of test steps and expected results |
| Structure | Ordered sequence of manual test steps, each pairing an action instruction with an expected result |
| MIME type | text/plain; XML variants also identified as application/xml |
| Associated OS | Windows |
| Primary tool | Microsoft Visual Studio Team System (Team Test edition) |
| Test execution model | Human-driven - a tester reads and performs each step manually; no code is executed by the file |
| Role in test project | Companion artifact to .vsmdi test metadata and .testsettings configuration files |
| Results output | Test run outcomes are saved separately as a .trx results file, not embedded in .mtx |
| Version binding | File schema tied to the Visual Studio Team Test version that authored it; not forward-compatible |
| Superseded by | Azure DevOps Test Plans and Microsoft Test Manager (MTM) work-item-based test cases |
| Extension collision | The .mtx extension is independently used by Matlab matrix files, The Sims body-shop files, and general math data formats |
| Editor compatibility | Viewable and editable in any plain-text or XML-aware editor (Visual Studio, Notepad, VS Code) |
| Released | Mid-2000s, with Visual Studio Team System / Team Test (Visual Studio 2005+) |
| Latest version | Legacy; manual testing later moved into Microsoft Test Manager (MTM) work items and Azure DevOps Test Plans |
| Specification | learn.microsoft.com |
MTX conversions
Community Q&A
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