Do Hyphens in URLs Really Impact SEO?

Why Are Spaces a Problem in a URL?

When a browser encounters a space in a URL, it automatically converts it to %20. This encoding mechanism transforms a readable URL like mysite.com/page name into mysite.com/page%20name.

The issue becomes evident when a user copies and pastes this link into an email, on social media, or in a document. The %20 string breaks readability and creates psychological friction: the URL appears technical, broken, and unreliable. Click-through rates suffer directly.

What’s the Difference Between a Hyphen and an Underscore?

Google recognizes two types of separators: the hyphen (-) and the underscore (_). The hyphen functions as a word separator for the search engine: seo-best-practices is interpreted as three distinct words.

The underscore, on the other hand, is treated as a connector: seo_best_practices becomes one composite keyword. This distinction dates back to Google's early years and remains valid. In practice, the hyphen has become the nearly universal standard on the web.

Does This Recommendation Only Apply to Main URLs?

No, the logic applies to any resource accessible via URL: content pages, PDF files, images, downloadable archives. Whenever a user can copy a link, readability matters.

The query parameters follow different rules: they naturally use special encodings. But for page slugs and file paths, hyphens remain the optimal standard.

• Spaces turn into %20 in browsers, making URLs unreadable
• The hyphen (-) separates words for Google, while the underscore (_) connects them
• URL readability impacts click-through rates and the perception of reliability
• This rule applies to pages, PDF files, images, and any shareable resource
• GET parameters (query strings) follow distinct encoding conventions

Does This Directive Really Reflect a Ranking Factor?

Mueller discusses link sharing and human readability, not direct ranking. Google has never stated that URLs containing %20 would be penalized in SERPs. The signal here is indirect.

A clean URL generates more organic clicks, more natural shares, and more citations without copying errors. These user behaviors feed signals of relevance and authority. The ranking factor isn't the URL itself; it's the engagement it facilitates or hinders.

Are There Exceptions in Practice?

Some CMSs or legacy platforms still generate URLs with encoded spaces. As long as the server returns a 200 response and the content is crawlable, Google indexes without issue. I’ve seen poorly structured sites rank on the first page with %20 everywhere.

Let’s be honest: it’s not the URL structure that saves them; it's the lack of strong competition for their queries. Once a competitor optimizes their URLs, the gap in CTR and social signals starts to show. [To be verified] on highly competitive transactional queries.

Should We Rewrite Existing URLs with %20?

Migrating URLs solely to replace %20 with hyphens requires 301 redirects. Each redirect marginally dilutes PageRank and imposes a crawl cost. If your site has thousands of pages with %20 but they are indexed and ranking well, it likely isn’t worth the effort.

However, for any new content or redesign, apply hyphens from the start. It’s a fundamental SEO best practice, just like HTTPS or alt tags. Not a magic factor, just an optimization that avoids unnecessary friction.

How Can I Audit Problematic URLs on My Site?

Use Screaming Frog or an equivalent crawler in full list mode. Export the "Address" column and filter for %20 in Excel or a text editor. You'll see immediately the affected pages and their volume.

Cross-reference this list with your high-traffic pages in Google Analytics or Search Console. If encoded URLs generate significant conversions, note them for potential planned redirects. If they are orphaned or low value, leave them as they are.

What Rule Should Be Applied for New Content?

Configure your CMS to automatically generate slugs with hyphens. WordPress, Drupal, Shopify, and most modern platforms do this by default. Just ensure that the automatic title-to-slug transformation properly replaces spaces and special characters with hyphens.

For uploaded files (PDFs, images), rename them before uploading: annual-report-2023.pdf instead of Annual Report 2023.pdf. Many servers retain the original name, including spaces, resulting in unnecessarily complex encoded URLs.

What If My Site Heavily Uses Underscores?

Underscores don’t break anything technically, but they glue words together in Google’s eyes. If your URL architecture uses guide_seo instead of guide-seo, you lose the chance for Google to interpret "guide" and "seo" as two distinct terms matching long-tail queries.

Migrating thousands of URLs from _ to - is a heavy decision. First, assess the impact: conduct an A/B test on a section of the site, measuring CTR and positioning variations over three months. If the gain is marginal, keep your current structure and focus on content. If the gain is significant, plan a gradual migration with well-mapped 301 redirects.

• Crawl your site and filter for %20 to identify encoded URLs
• Configure your CMS to automatically generate slugs with hyphens (-)
• Rename files before upload: replace spaces and special characters with hyphens
• If migration is needed, plan clean 301s and monitor Search Console for 90 days
• Test CTR gains on a sample before generalizing a URL overhaul
• Incorporate this rule into your editorial checklist for all new content