Discussions

When developers talk about improving existing code, two terms often come up: refactoring and rewriting. While they may sound similar, they represent very different approaches—and choosing the wrong one can lead to wasted time and unnecessary risk. To clearly understand the difference, it helps to start with how most teams refactoring define the concept: refactoring means improving the internal structure of code without changing its external behavior. The goal is cleaner, more readable, and more maintainable code.

Refactoring is usually incremental. You might rename variables, break long functions into smaller ones, remove duplication, or simplify logic. Because behavior stays the same, refactoring is generally safer—especially when backed by solid unit tests. It’s ideal when the code works but has become messy, hard to understand, or difficult to extend. Over time, regular refactoring helps reduce technical debt and keeps the codebase healthy.

Rewriting, on the other hand, means starting over. You discard most (or all) of the existing code and build a new solution from scratch. This is typically done when the current system is deeply flawed, built on outdated assumptions, or no longer meets business needs. While rewriting can feel refreshing, it carries higher risk: missed edge cases, longer development cycles, and the danger of reintroducing bugs that were already solved in the old system.

In practice, refactoring should almost always be your first option. It preserves existing knowledge embedded in the code and allows gradual improvement with less disruption. Rewriting should be a last resort, chosen only when incremental improvements are no longer feasible.

Modern tools and practices also make refactoring safer than ever. For example, tools like Keploy can help ensure application behavior remains consistent while internal changes are made.

In short, refactor when you want to improve how the code works internally, and rewrite only when you truly need to change what the system is at its core.