4 ways to familiarize yourself with a new codebase
Starting with a new project can feel overwhelming. Whether you’re joining a new team, contributing to open source, or inheriting an existing application, learning how to navigate and understand the codebase quickly is critical. Below are four practical steps you can take to get comfortable with unfamiliar code.
1. Understand What the Codebase Is Supposed to Do
Before diving into the code, first answer this question: what problem does the application solve?
- Review features, business logic, and user flows to understand the bigger picture.
- Leverage AI tools to generate a “business logic” summary of the code and documentation.
- Combine what you learn into a clear overview of the codebase’s responsibilities and goals.
📌 Pro tip: Ask stakeholders, read the README, check product docs, and play with the live app if available.
2. Get a High-Level Application Design Overview
Once you understand the purpose, zoom out to see the architecture:
- Use AI to help explain file structures, frameworks, and infrastructure.
- If possible, talk to someone knowledgeable (a senior dev, tech lead, or architect).
- Organize your findings into concise architecture documentation you can reference later.
📌 This helps you avoid getting lost in the weeds and gives context for where code fits in the bigger picture.
3. Run the Code Locally and Debug the Flow
Nothing beats seeing the code in action.
- Set up the project locally and make sure it runs.
- Debug step-by-step to trace inputs, outputs, and data flows.
- Don’t be surprised if the docs are outdated—running the code reveals the truth.
📌 Pro tip: Start with simple flows (like user login or homepage load) before moving to deeper functionality.
4. Review Previous Code Changes
History often tells you more than the present.
- Explore merge requests, issues, and commit history.
- Look for patterns: Are changes frequent or rare? Are bugs common? Is this legacy or greenfield code?
- Spot potential red flags (large unreviewed PRs, lack of tests, or messy commit histories).
📌 This helps you understand not just how the code works, but how it has evolved over time.
Final thoughts
Familiarizing yourself with a new codebase takes time, but following these four steps will give you a strong foundation:
- Know what the app does.
- Learn the architecture.
- Run/debug it locally.
- Review its history.
💬 Question for you: How do you approach a new codebase? Do you have a step 5 worth adding?
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