Microsoft Application Inspector is an open-source source code characterization tool that reports what a codebase actually contains, from cryptography and shell calls to cloud APIs, so teams can assess third-party components before trusting them.
Microsoft Application Inspector is a command-line analyzer that characterizes source code rather than hunting for bugs. It scans a project, or a compressed copy of one, against a rule set built from library and API patterns, then reports the features it recognises: cryptographic routines, file and shell operations, cloud service calls, frameworks and more. The default run writes an HTML report, while JSON, text, SARIF and Markdown outputs suit pipelines and reviews. Its purpose is to answer one question quickly, what does this software actually do, so that a component can be assessed from its own source instead of from documentation that may be thin, outdated or optimistic.
Microsoft Application Inspector deliberately avoids the fault-finding language that vulnerability scanners use. It does not decide whether a pattern is good or bad; it reports matches with a severity label and a confidence value, leaving the judgement to a reviewer. That design makes it useful well beyond security work, from checking which dependency dragged in an unexpected networking library to confirming that only approved cryptographic algorithms appear in a release. Its value also shows up before adoption: unlike packaging-side helpers such as the AppInstaller File Builder, which prepare an application for delivery, this tool inspects the code you are about to depend on. The project is open source and available both as a command-line tool and as a library.
The benefit of Microsoft Application Inspector is that it replaces educated guessing with a list of things that were actually found. When a team evaluates a third-party library, the usual options are reading documentation, trusting a reputation score or skipping the question entirely, and none of those scale across hundreds of dependencies. Microsoft Application Inspector reads the source instead and returns named features with the files and lines that triggered them, which makes the review concrete and fast. Its tag comparison command is the part security reviewers tend to appreciate most, because running it across two versions of the same component shows exactly which capabilities appeared between releases, a check that catches injected functionality as well as unintended drift. Because rules are plain files, organisations can encode their own standards and run the scan inside a build pipeline.
Key capabilities and highlights.
The bundled rule set recognises hundreds of coding patterns drawn from well-known libraries and APIs, covering areas such as encryption, file and shell operations, cloud service calls and UI frameworks. Scans span many languages, including C, C++, C#, Java, JavaScript, Python, Go, Ruby and PowerShell, and mixed-language projects are handled in a single pass.
Every match carries a severity label and a confidence value, and both can be filtered at the command line so a review opens with the critical, high-confidence findings rather than a wall of noise. Rules can also flag items for manual review, which separates clear evidence from anything that needs a human eye.
A dedicated comparison command in Microsoft Application Inspector scans two source trees and reports the differences in detected tags, so you can see which capabilities were added or removed between releases. Applied to an updated dependency, it is one of the fastest ways to spot unexpected new behaviour.
Results can be written as an HTML report for reading, plain text for logs, JSON for further processing, Markdown for pull request comments, or SARIF for code scanning dashboards. Choosing the format at run time means a single scan can satisfy both a human reviewer and an automated pipeline.
Rules live in editable files, so organisations can add detection patterns for their own frameworks and internal APIs, or restrict a scan to a curated set. A separate command validates custom rules, including their self-test match and non-match cases, before those rules ever touch real source.
A utility command lists every tag the current rule set can detect without scanning any code, giving reviewers a catalogue of exactly what the tool looks for. That list doubles as reconnaissance when writing new rules, because it shows the naming conventions and available categories at a glance.
Source can be supplied as a directory, an individual file, or a compressed archive, so a release package can be inspected without unpacking it first. Exclusion patterns keep build output, version control folders and test directories out of the scan, while configurable timeouts stop a large repository from running away.
Sensible exit codes, SARIF output and a Markdown summary make the tool straightforward to embed in continuous integration. Reporting tags alone, or capping how many matches are collected per tag, keeps runs quick, so a scan can gate a pull request instead of becoming an occasional manual chore.
Browse historical releases and previous builds.
Common questions about Microsoft Application Inspector.
It is an open-source source code characterization tool from Microsoft. It scans a codebase against a rule set built from library and API patterns and reports the features it finds, such as cryptography, file access, shell execution and cloud service calls.
No. Microsoft Application Inspector deliberately does not classify patterns as good or bad. It reports what it detected, along with severity and confidence labels, so a reviewer can judge whether those features are expected for that particular component.
Scans cover a broad set of languages, including C, C++, C#, Java, JavaScript, HTML, Python, Objective-C, Go, Ruby and PowerShell. A project containing files in several languages can be analysed in one run rather than language by language.
Use the tag comparison command with two source paths, an older release and a newer one. It reports differences in the detected features, which highlights capabilities that appeared in the newer version and deserve a closer look.
Yes. Rules are stored in editable files and custom rule locations can be supplied to a scan. A validation command checks syntax and optional self-tests, so broken or ambiguous rules are caught before a real analysis run.
HTML is the default for interactive reading, with JSON, plain text, Markdown and SARIF available for automation, dashboards and other reporting tools that consume structured results.
Yes. A compressed archive can be supplied as the source and archive enumeration is enabled by default, so a release package can be examined without extracting it first. Crawling can also be turned off when only loose files should be considered.
It is free and open source, published by Microsoft, and usable both as a command-line tool and as a library that can be called from your own code and automated tooling.
Microsoft Application Inspector is an open-source source code characterization tool that reports what a codebase actually contains, from cryptography and shell calls to cloud APIs, so teams can assess third-party components before trusting them.
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