What You'll Learn
How to use AI to decode any piece of code you did not write — whether it is legacy code from a previous developer, an open-source library, a snippet from Stack Overflow, or something a colleague produced — and understand exactly what it does.
Why This Matters
Reading someone else's code is often harder than writing your own. Without comments, without context, and without knowing the original developer's intention, even experienced programmers can spend hours deciphering a 30-line function. AI can read code and explain it in plain English in seconds — identifying what each section does, why it is structured that way, and what edge cases it handles (or fails to handle).
Step-by-Step Guide
Step 1: Ask for a plain-English explanation
Please explain what this code does in plain English. Assume I understand basic programming concepts but am not familiar with this specific pattern or library.
[paste the code here]
Step 2: Break it down line by line (for complex code)
Go through this code line by line (or block by block) and explain what each part does. Highlight anything unusual, clever, or potentially problematic.
[paste the code]
Step 3: Ask about specific parts you do not understand
In the code above, I don't understand what [specific line or section] is doing. Can you explain it more clearly, and give me an analogy if it helps?
Step 4: Ask what could go wrong
Are there any edge cases, potential bugs, or situations where this code might behave unexpectedly? What inputs or conditions could cause it to fail?
Step 5: Ask for refactoring suggestions (optional)
If you need to work with the code going forward:
Is this code written in a modern, idiomatic style? Are there any improvements or simplifications you would recommend that preserve the same behaviour?
Tips for Better Results
- Include the language and framework. "This is Python using the pandas library" or "This is JavaScript in a Next.js API route" helps AI give more accurate explanations.
- Provide context about where the code runs. "This runs when a user submits a form" or "This is a scheduled background job" helps AI explain the code's purpose more clearly.
- Ask for a summary first, then detail. Start with "What does this do overall?" before asking for line-by-line detail. The high-level summary helps the detail make sense.
Tools That Work Best for This
- Claude — exceptional at code explanation and particularly good at understanding complex, multi-step logic. Produces clear, well-structured explanations with helpful analogies.
- ChatGPT — also strong, especially for popular frameworks and widely-used patterns. Good at drawing on its knowledge of best practices to contextualise what the code is doing.