Practical paths into unfamiliar code

Every engineer eventually faces an unfamiliar codebase. Between accumulated design patterns, bug fixes, and temporary workarounds, even well-maintained systems can be daunting to approach. When GitHub engineer Brittany Ellich moved to a new team last year, she asked her colleagues how they navigate this challenge. Their answers form a practical toolkit for learning any new technical environment.

Start with code exploration

  • Tackle “Good First Issues.” These well-scoped tasks are often selected by the owning team specifically to help newcomers learn key components without becoming overwhelmed. They provide a natural entry point into the system while delivering immediate value.
  • Use GitHub Copilot as a learning aid. Open Copilot Chat alongside the codebase and ask targeted questions. The /explain function can help clarify confusing sections. Useful queries include asking what a function returns for a given input, requesting a summary of a method's purpose, and identifying gaps in existing test coverage.
  • Inspect telemetry and metrics. Production data reveals how the application actually behaves—patterns during peak usage, which components get the most attention, and where the system needs work. This data-driven context is often more informative than reading code in isolation.
  • Learn through testing. Write new tests to verify assumptions, make deliberate modifications, and break things in development to observe failure modes. This builds a feel for the system's boundaries.

Accelerate through collaboration

  • Pair actively. Rather than just observing, ask questions about workflows, note frequently accessed files, and examine debugging strategies. Even passive participation surfaces context about how components interconnect.
  • Dig into the “why.” When receiving tasks, understand their business rationale and technical motivation. Asking apparently basic questions often reveals crucial insights that inform better architectural decisions.
  • Stay tethered to team channels. Monitor chat rooms and incident responses. Observing how alerts are handled teaches common failure patterns and builds experience for managing real incidents.

Write to solidify understanding

  • Keep personal documentation. Maintain a living record of discoveries, questions, and insights about code paths, architectural decisions, and system interfaces. This becomes a personal reference and exposes gaps in comprehension.
  • Build technical maps. Draw diagrams of architecture, data flows, and entity relationships. Start with high-level “black boxes” and fill in details progressively. Visualizing systems often reveals hidden patterns—tools like Figma work well for iterating on these maps as understanding deepens.
  • Track commands and workflows. Record useful commands and scripts with context on when and why to use them. A cheat sheet is particularly valuable for complex build systems and pipelines.
  • Understand the domain. Learn from product owners, customer insights, and industry best practices. Knowing what matters most to users in that space is key to understanding the codebase itself.

Teach what you learn

Teaching others verifies your grasp of a codebase. Personal documentation can be formalized into resources for future team members, forcing you to structure your knowledge and reveal incomplete understanding. When documentation has gaps, improving it both benefits the next person and validates your understanding with current experts—GitHub's markdown guide serves as a useful starting point for writing clear documentation.

Reflecting regularly on key questions also helps consolidate learning:

  • Can you describe the system in a few concise sentences?
  • How does it interact with adjacent systems?
  • What surprised you most while learning?
  • What aspects remain unclear?

Documentation is often favored learning method—it forces structure and exposes gaps. A template Ellich developed for learning new codebases is available as a public gist, designed to work alongside these strategies. Whatever your approach, mastering a new codebase takes time; those looking to brush up on GitHub fundamentals can find beginner-friendly resources in the GitHub for Beginners video series.