URLs: Dash vs. Underscore – Which Convention Wins?

The design of a URL is more than just a stylistic choice; it touches upon user experience, Search Engine Optimization (SEO), and underlying technical compatibility. When developers encounter the debate between using hyphens (-) and underscores (_) in slugs or path segments—such as /about-us versus /about_us—it often boils down to convention versus pure technical necessity.

Is it better convention to use hyphens or underscores in your URLs? Should it be <code>/about_us</code> or <code>/about-us</code>?

The Usability Argument: Readability First

From a purely end-user and readability perspective, the answer is overwhelmingly in favor of hyphens. When a user reads a URL aloud, or when they see it in a navigation bar, hyphens naturally separate words, making the path much easier to parse visually.

For example, /about-us is immediately recognizable as "about us." Underscores, while perfectly valid characters in URLs (as they are not reserved), often carry a connotation from programming languages, specifically snake_case, which developers use for variable and function naming. Mixing these conventions can introduce unnecessary cognitive load for the average visitor.

The Technical & SEO Perspective

While usability favors hyphens, we must also consider how search engines and server-side frameworks interpret these structures.

Hyphens and SEO

Search engines like Google treat hyphens as word separators when indexing URLs. They function as a clear delimiter between words, which aids in understanding the topic of the page. This is crucial for generating effective SEO-friendly slugs. A cleaner URL structure generally leads to better crawling and ranking opportunities.

Underscores and Compatibility

Underscores are perfectly valid URL characters and do not inherently cause compatibility issues across modern web systems or JavaScript frameworks. However, in some legacy systems or specific database contexts, underscores might be handled differently than hyphens, making the hyphen the safer, more universally compatible choice for routing and parsing.

Framework Context: Where Convention Meets Code

In modern PHP frameworks, such as Laravel, URL routing handles these differences seamlessly. When you define a route, the framework is designed to handle standard HTTP path conventions. Whether you are dealing with file paths or clean public-facing URLs, adhering to established web standards (like using hyphens for readability) simplifies maintenance down the line.

When developing robust applications, consistency is paramount. If your application uses snake_case internally for database columns or class names, it’s often best to maintain that convention where it makes sense, but reserve hyphenated slugs for publicly accessible URLs. This separation keeps code clean while optimizing for user experience. For instance, when setting up routes in a Laravel application, the routing system is designed to handle these URL segments effectively, allowing developers to focus on the business logic rather than path syntax.

Best Practice Recommendation

The consensus recommendation for public-facing URLs is to use hyphens. They offer superior readability and align better with established web conventions recognized by browsers and search engines.

However, always maintain consistency within your project. Decide early whether the segment represents a programmatic concept (use snake_case internally) or a human-readable path (use kebab-case externally). For URLs, prioritize the human reader experience.

Conclusion

The debate between dashes and underscores in URLs is ultimately a balance between developer style and end-user experience. While both are technically permissible, hyphens (-) are the superior choice for creating clean, readable, and SEO-friendly public-facing URLs. By prioritizing readability, you ensure that your site is accessible to everyone, while reserving other conventions for internal code structure.

Stefan

SEO engineer and Laravel developer. Building tools to help Laravel applications rank higher in search results.