Joern Documentation

Platform for C/C++ Code Analysis based on Code Property Graphs

Joern is a platform for robust analysis of C/C++ code. It generates semantic code property graphs, a graph representation of code for cross-language code analysis. Semantic code property graphs are stored in a custom graph database. This allows code to be mined using search queries formulated in a domain-specific query language based on the graph traversal language Gremlin. Joern provides a peek into the underlying technology that powers the commercial code analyzer Ocular.

The core features of Joern are:

  • Fuzzy Parsing of C/C++. Joern employs a fuzzy parser for C/C++ based on the concept of Island grammars. The parser enables importing arbitrary code even if a working build environment cannot be supplied or parts of the code are missing.
  • Semantic Code Property Graphs. Joern creates semantic code property graphs from the fuzzy parser output and stores them in an in-memory graph database. SCPGs are a language-agnostic intermediate representation of code designed for query-based code analysis. For background information on code property graphs, we strongly encourage you to read the original paper on the topic ( and the specification of the semantic CPG at .
  • Intelligent Search Queries. Joern offers a stronly-typed Scala-based extensible query language for code analysis based on Gremlin-Scala. This language can be used to manually formulate search queries for vulnerabilities as well as automatically infer them using machine learning techniques.
  • Extendable via CPG passes. Semantic code property graphs are multi-layered, offering information about code on different levels of abstraction. Joern comes with many default passes, but also allows users to add passes to include additional information in the graph, and extend the query language accordingly.