Should you really prefer hyphens over underscores in your URLs?

What is Google's reasoning behind the distinction between hyphens and underscores?

The reason is historical and relates to how search engines were designed. Hyphens (-) are treated as natural spaces between words, allowing the engine to analyze each term separately.

Underscores (_), on the other hand, come from a programming convention where they are used to create variable or function names without spaces. Google therefore interprets them as characters that are integral to the word, not as separators.

What are the real differences for crawling and indexing?

For example, the URL example.com/running-shoes-women will be broken down into three distinct terms: "running", "shoes", "women". The engine can thus understand that the page is about shoes AND running AND women.

In contrast, example.com/running_shoes_women will be read as a single token "runningshoeswomen". Google will not be able to associate this URL with queries containing only "running shoes" or "shoes for women". The semantic relevance of the URL is therefore lost.

Is this recommendation set in stone or likely to evolve?

Google explicitly states that "this could change in the future". This mention indicates that the company acknowledges the current technical limitation and does not elevate it to an absolute principle.

In practice, the engine is becoming increasingly efficient at understanding the context of a page regardless of its URL. But until an official announcement confirms a change, it would be unwise to ignore this established best practice.

• Hyphens are viewed as word separators, facilitating semantic analysis of the URL
• Underscores are treated as internal characters, making the URL opaque to the engine
• This rule applies to all URLs: pages, categories, articles, product sheets
• Google implies that this constraint could evolve, but no timeline is specified
• The real impact is measured on the semantic understanding of your URLs by the engine, not on a direct ranking factor

Is this statement consistent with real-world observations?

Yes, completely. Empirical tests have shown for years that URLs with hyphens receive better keyword recognition. SEO analysis tools accurately detect terms separated by hyphens, whereas they struggle with underscores.

However, let's clarify: the URL remains a weak signal in Google’s overall algorithm. A page with underscores but excellent content and strong backlinks will always outperform a mediocre page with perfect hyphens. An optimized URL is a bonus, not a magic wand.

In what situations does this rule pose real problems?

The real challenge is migration. If your site has existed for years with underscores in all URLs, changing now involves massive redirects. The risk of temporary traffic loss or technical errors may outweigh the expected benefit.

Another tricky situation: some CMS or frameworks automatically generate URLs with underscores for technical compatibility reasons. Modifying this behavior often requires costly custom development. You must weigh the actual ROI: if your pages already rank well, the urgency is low. [To check] on a case-by-case basis, depending on your performance history.

Can we really count on a future evolution from Google?

Let's be frank: Google has been saying "this could change" for years without any movement. This phrasing is a typical safeguard clause, not a promise of action. The engine has priorities far more strategic than recoding its URL parser.

In practice, as long as no Google Search executive publicly takes a stance with a timeline, consider that the current rule will endure. Basing your strategy on a hypothetical change would be unwise. Hyphens remain the recommended standard, period.

What should I do if my site already uses underscores?

First step: assess the scope of the problem. How many URLs are affected? What is their weight in your organic traffic? If they are a few secondary pages, the impact is negligible. If it's your entire structure, the question deserves analysis.

For a site established with underscores, a drastic migration presents risks. Massive 301 redirects can cause ranking fluctuations for several weeks. If your pages perform well, urgency is not a priority. Focus first on content and backlinks.

How should I structure URLs for new projects?

For any new site or redesign, consistently adopt hyphens. It’s simple, clean, and in line with official recommendations. Configure your CMS or URL generator to automatically replace spaces with hyphens.

Pay attention to details: avoid multiple consecutive hyphens ("word--another" looks ugly and is unnecessary), and ban hyphens at the start or end of URLs. A structure like /category/sub-category/main-keyword remains the optimal standard. No need to complicate things.

What technical checks should I perform regularly?

Audit your automatically generated URLs, especially after CMS or plugin updates. Some modules may reintroduce underscores without warning. A monthly crawl with Screaming Frog or equivalent is enough to detect anomalies.

If you identify mixed URLs (some with hyphens, others with underscores), gradually harmonize starting with the pages that have high potential: landing pages, main categories, pillar articles. These structural optimizations can be complex to deploy without errors, especially on large sites. Hiring a specialized SEO agency can help secure these technical migrations and provide tailored support suited to your context.

• Crawl your site to identify all URLs containing underscores
• Prioritize strategic pages for a possible gradual migration
• Configure your CMS to automatically generate hyphens instead of spaces
• Test your 301 redirects before any massive URL migration
• Monitor your rankings and traffic for 4 to 6 weeks post-migration
• Document your naming convention to maintain consistency over time