Skip to main content

How to Understand a New Codebase

You've been handed access to a repository with 50,000+ lines of code. No documentation. The original authors are gone. Where do you even start?

This guide will give you a systematic approach to understanding any codebase.

Quick Answer​

Understanding a new codebase takes 2-4 weeks on average, but you can make meaningful contributions within 3-5 days using the right approach.

The Systematic Approach​

Step 1: Get It Running (Day 1)​

Before reading any code, get the application running locally.

# Clone and install
git clone <repo>
cd <repo>
npm install  # or pip install, cargo build, etc.

# Run it
npm start

# Run tests
npm test

Why this matters: Running the app gives you concrete behavior to map back to code. Reading code without running it is like reading sheet music without hearing the song.

Step 2: Find the Entry Points (Day 1-2)​

Every application has entry points—where execution begins:

TypeCommon Entry Points
Web appindex.html, App.js, main.tsx
Backendmain(), server.js, app.py
CLIbin/, cli.js, __main__.py
LibraryExported functions in index.js or lib/

Start here and trace the flow forward.

Step 3: Identify Core Data Models (Day 2-3)​

Find where the main entities are defined:

  • Database schemas
  • TypeScript interfaces
  • Class definitions
  • API response types

Understanding the data model is understanding half the system.

Step 4: Trace One Request End-to-End (Day 3-4)​

Pick one user action and follow it through the entire system:

  1. User clicks button →
  2. Frontend handler →
  3. API call →
  4. Backend route →
  5. Business logic →
  6. Database query →
  7. Response →
  8. UI update

Document this flow. It's your map for understanding everything else.

Step 5: Map the Architecture (Week 1-2)​

Create a mental (or actual) diagram of:

  • Major components/modules
  • How they communicate
  • External dependencies
  • Data flow

What to Look For​

Folder Structure Patterns​

src/
├── components/     # UI components
├── pages/          # Route handlers
├── services/       # Business logic
├── models/         # Data models
├── utils/          # Helpers
└── api/            # External integrations

Naming Conventions​

  • How are files named? (UserService.ts vs user-service.ts)
  • How are functions named? (getUserById vs get_user_by_id)
  • What patterns do they follow? (Repository pattern? MVC? Hexagonal?)

Configuration Files​

These reveal a lot about a project:

FileReveals
package.jsonDependencies, scripts, project structure
tsconfig.jsonTypeScript setup, path aliases
.env.exampleRequired environment variables
docker-compose.ymlServices and infrastructure
MakefileCommon operations

Common Challenges​

1. No Documentation​

Solution: Use Ramp to generate documentation automatically:

ramp guide

This creates an ONBOARDING.md with architecture overview, key concepts, and common tasks.

2. Spaghetti Code​

Solution: Focus on the happy path first. Ignore error handling, edge cases, and legacy code until you understand the core flow.

3. Missing Context​

Solution: Use git log and git blame to understand why code was written:

# Who wrote this and why?
git blame src/auth/login.ts

# What changed recently?
git log --oneline -20

# What was the context for this change?
git show <commit-hash>

4. Unfamiliar Technology​

Solution: Don't try to learn the framework AND the codebase simultaneously. Learn the framework basics first (30 minutes of tutorials), then return to the codebase.

Tools That Help​

# Voice-powered codebase exploration
ramp voice
> "How does authentication work in this codebase?"
> "Where are database migrations handled?"
> "What's the pattern for adding new API endpoints?"

Traditional Tools​

  • IDE search — Cmd+Shift+F to search across files
  • Call hierarchy — Right-click → "Find All References"
  • Debugger — Set breakpoints and step through code
  • Dependency graph — madge (JS), pydeps (Python)

Timeline Expectations​

Experience LevelBasic UnderstandingFull Productivity
Junior4-8 weeks3-6 months
Mid-level2-4 weeks1-3 months
Senior1-2 weeks2-4 weeks

These can be cut in half with Ramp's AI-powered assistance.

Facing a new codebase? Try Ramp free →