Have you ever added a feature because you might need it someday?

Or built an abstraction for a use case that doesn't exist yet?

Or created extra flexibility that no one has ever used?

If so, you’ve broken one of the most pragmatic principles in software development: YAGNI, which stands for You Aren’t Gonna Need It.

Let’s unpack what this principle means, why it’s often ignored, and how following it can keep your codebase focused, lean, and easier to maintain.

What Is the YAGNI Principle?

“Always implement things when you actually need them, never when you just foresee that you need them.” — Ron Jeffries, co-founder of Extreme Programming

YAGNI is a principle that encourages you to resist the temptation to build features or add flexibility until you are absolutely sure you need them.

In simple terms: Don’t build for tomorrow. Build for today.

The Real-World Problem

Suppose you are working on a project that involves uploading user profile pictures.

Your current requirement is simple:

• Accept an image
• Resize it
• Store it

But you start thinking ahead.What if:

• Tomorrow we need support for video uploads?
• We may want to switch from local file storage to cloud storage?
• We could support 3D avatars?

So you build a flexible, pluggable, extensible media-processing engine. You introduce interfaces, dependency injection, multiple handler classes, and a storage abstraction layer.

All of this before your first user even uploads a profile photo.

What’s the result?

• A bloated, overly complex system
• Slower delivery of the core functionality
• More code to test, maintain, and debug
• Features no one asked for

This is a classic case of violating the YAGNI principle.

A Simpler Way with YAGNI

Let’s revisit the image upload feature and apply the YAGNI principle.

The Needed Functionality

This code:

• Meets today’s needs
• Is easy to read and test
• Can be extended later, when necessary

If the requirement to support cloud storage or video formats arises, that’s the time to refactor and extend—not before.

When to Bend the Rule

Like all principles, YAGNI has exceptions. Sometimes, planning ahead is justified.

Here are cases where it’s acceptable to go beyond current needs:

• Security and compliance requirements: You may need to prepare for data protection, auditing, or regulatory constraints up front.
• Architecture with known long-term constraints: For example, if you are writing code for a high-availability system, some abstractions or patterns may be required from day one.
• Reusable libraries or frameworks: If you are building tools for other developers, some flexibility may be expected.

Even then, be cautious. Avoid building for imagined scenarios.

Final Thought

Software is not built to be perfect on day one. It is built to evolve.

The YAGNI principle reminds us to stay grounded in reality. Code for what is needed now. When the time comes to evolve or extend, you will have the clarity and simplicity to do it well.

So next time you think:

“Let’s add this now, just in case…”

Pause, and ask yourself: “Is there a real need for this today?”

If not, then you probably aren’t gonna need it.