Picture this: you're staring at code you wrote six months ago, trying to understand what on earth Past You was thinking. The variable names make sense, the logic flows correctly, but something crucial is missing—the why behind your decisions. This is where good comments transform from nice-to-have into essential documentation.

Comments are more than explanations; they're conversations with your future self and your teammates. The best developers don't just write code that works—they write code that tells its own story through strategic, well-placed comments that illuminate intent rather than describe syntax.

Most beginners write comments that mirror their code: 'increment counter by one' sits above counter++. These comments add zero value because the code already says what it does. The real magic happens when you explain why you're incrementing that counter—what business logic or user need drives this decision.

Consider these two comments for the same retry logic: 'Retry three times' versus 'Retry three times because network hiccups are common but four attempts indicate a real problem.' The second comment prevents someone from casually changing that three to ten without understanding the consequences. It captures the reasoning that led to this specific implementation choice.

The best comments answer questions that code alone cannot: Why this algorithm over another? What edge case does this handle? What assumption are we making about the data? These insights are what disappear from memory first, making them the most valuable things to document. When you find yourself making a non-obvious choice, that's your cue to leave a comment explaining your reasoning.

Takeaway

Before writing a comment, ask yourself: 'Could someone understand what this code does by reading it?' If yes, skip the comment. If they could understand what but not why, that's where your comment belongs.

Not all code needs comments, and over-commenting can be as harmful as under-commenting. The key is identifying inflection points—places where understanding breaks down without additional context. These typically include complex algorithms, workarounds for external system quirks, performance optimizations that sacrifice readability, and business logic that seems arbitrary without domain knowledge.

Focus your commenting energy on code boundaries: where your system interfaces with external APIs, where data transforms between layers, and where important decisions affect system behavior. A well-placed comment at a module's entry point explaining its overall purpose and main assumptions can prevent hours of confusion. Similarly, document any 'magic numbers' or thresholds—that timeout of 30 seconds probably has a reason behind it that should be captured.

Another critical area for comments is negative space—explaining what you're not doing and why. 'We don't validate email format here because the mail service does it more thoroughly' prevents well-meaning developers from 'fixing' what looks like missing validation. These comments protect your design decisions from being undone by someone who doesn't have your current context.

Takeaway

Comment at system boundaries, decision points, and anywhere the code alone doesn't tell the complete story. If you struggled to understand something while writing it, future readers will struggle too—that's where a comment helps most.

Outdated comments are worse than no comments—they actively mislead developers and erode trust in all documentation. The comment says the function returns null on error, but it actually throws an exception. Someone reads the comment, codes accordingly, and introduces a bug. This happens because we treat comments as write-once artifacts instead of living documentation that needs maintenance alongside code.

The solution isn't to avoid comments but to write them in ways that resist decay. Link comments to code structure so they break obviously when things change. Instead of 'Process the first three elements,' write 'Process elements up to MAX_BATCH_SIZE.' When MAX_BATCH_SIZE changes, the comment remains accurate. Avoid duplicating information that exists elsewhere—reference documentation, ticket numbers, or design docs rather than reproducing their content.

Make comment maintenance part of code review culture. When reviewing code changes, explicitly check if existing comments still make sense. If you're changing behavior, search for comments that might need updates. Better yet, write comments that explain principles and constraints rather than implementation details. 'We process in batches to avoid memory overflow' stays true even if batch size changes.

Takeaway

Write comments that explain principles and constraints rather than implementation details. During code reviews, treat comment updates with the same importance as code changes—outdated comments are bugs waiting to happen.

Comments are your code's narrative voice, explaining the story behind the syntax. They bridge the gap between what code does and why it exists, saving countless hours of detective work for everyone who touches your code—including Future You.

Master the art of strategic commenting: document intent over implementation, focus on critical decision points, and maintain comments like you maintain code. Your future self will thank you when that cryptic piece of logic suddenly makes perfect sense.