The Original Reason Hyphens Won

The advice to use hyphens rather than underscores in URLs comes from how early search engines tokenised text. A hyphen was interpreted as a word separator, meaning a URL segment containing hyphenated words was read as several distinct words. An underscore was treated as a word character, meaning the same segment joined into one long token that matched nothing a user would ever search for.

In practice this meant that a URL using hyphens gave a search engine several recognisable keywords, while the underscore version gave it one meaningless string. Since URL words contribute a modest relevance signal, hyphens had a real if small advantage. That is why every style guide, content management system default and technical audit has recommended hyphens for the better part of two decades.

How AAMAX.CO Approaches URL Structure and Site Migrations

We are AAMAX.CO, a full service digital marketing company providing web development, digital marketing and SEO services to clients worldwide. URL structure is one of those details that is trivial to get right at build time and expensive to change later, so we plan it deliberately on every project. When we inherit a site with inconsistent or messy URLs, we assess honestly whether changing them is worth the risk, and where it is, we execute the migration with complete one-to-one redirect mapping, internal link updates, sitemap regeneration and post-launch indexation monitoring. When it is not worth it, we say so rather than manufacturing work. If you are planning a rebuild or worried about a restructure, our SEO services cover the whole process safely.

How Much Does It Actually Matter Now

Modern search engines are considerably better at understanding URLs than they were when this guidance originated. They can often infer word boundaries from context, and the relevance contribution of URL keywords is small compared with content quality, page experience, internal linking and authority. An excellent page on an underscore URL will comfortably outrank a mediocre page on a hyphenated one.

So the honest assessment is this: hyphens remain the correct choice for new URLs, and there is no reason to choose otherwise, but underscores in existing URLs are a minor imperfection rather than a serious problem. If you are auditing a site and find underscores, they belong near the bottom of your priority list, well below indexation problems, thin content, slow pages and weak internal linking.

Should You Change Existing URLs

This is the question that matters practically, and the default answer is no. Changing URLs always carries risk. Every redirect adds a small amount of latency, every migration risks broken links, and every restructure can cause temporary ranking volatility. Doing that to convert underscores into hyphens on pages that already rank means accepting real downside for a marginal theoretical gain.

There are situations where changing is justified. If you are already undertaking a redesign or platform migration that will change URLs anyway, standardise on hyphens as part of that work since the risk is already priced in. If a page has no rankings, no traffic and no external links, changing its URL costs nothing. If your URLs are so badly formed that they are genuinely unreadable, containing session identifiers, deep parameter chains or database keys, the improvement is worth the migration.

If you do change URLs, implement permanent redirects mapping each old URL to its specific new equivalent. Never redirect a batch of pages to a homepage or category page, because that destroys the relevance signals. Update internal links in the content itself rather than relying on redirects, regenerate your sitemaps, and monitor your indexation reports closely for several weeks afterwards.

What Good URL Structure Looks Like

Beyond the separator question, several principles produce URLs that serve both users and search engines well. Keep them short. A concise URL is easier to read, easier to share, easier to remember and less likely to be truncated in search results or messaging apps.

Make them descriptive. Someone should be able to guess what a page contains from its URL alone. This helps click-through from search results and helps anyone deciding whether to follow a shared link.

Use lowercase consistently. Some server configurations treat differing cases as different URLs, which creates duplicate content and confusing analytics. Enforce lowercase at the server level so there is only ever one valid form.

Remove filler words. Articles, conjunctions and prepositions add length without adding meaning in most cases, though you should keep them where removing them makes the URL genuinely ambiguous or awkward.

Keep the folder depth shallow. Deeply nested paths suggest content buried far from the homepage and are harder to read. Two or three levels is usually plenty for even large sites.

Avoid dates in URLs for evergreen content. A date in the path makes an article look stale the following year and prevents you from updating and republishing without a migration.

Decide on a trailing slash convention and enforce it, since both versions resolving independently is a common and avoidable duplication issue.

Other Separators to Avoid

Spaces in URLs get encoded into unreadable character sequences and should never be used. Plus signs are interpreted as spaces in query strings and cause confusion in paths. Camel case relies on capitalisation to signal word boundaries, which conflicts with the lowercase rule and is unreliable. Concatenating words with no separator at all produces strings that are hard to read and easy to misparse. Hyphens remain the only separator with no drawbacks.

One caveat on hyphens: do not overdo them. A URL with eight or nine hyphenated words looks manufactured and stuffed. Aim for three to five meaningful words in the final segment.

Consistency Above All

The most valuable habit is consistency. A site where some URLs use hyphens, some use underscores, some include dates and some do not is harder to maintain, harder to audit and more likely to accumulate duplicate variants. Document a single convention, apply it in your content management system defaults, and enforce it in review.

Going forward, every new URL should follow the standard. Existing URLs can be left alone unless there is a broader reason to change them.

The Verdict

Underscores are technically suboptimal but not seriously harmful. Use hyphens for everything new, because there is no cost to doing so and a small benefit. Leave existing underscore URLs in place unless you are already migrating for another reason, since the redirect risk usually outweighs the gain. Spend your effort on the factors that move rankings substantially: content depth, search intent alignment, internal linking, technical health and genuine authority.

If you would like a technical audit that separates the issues genuinely costing you traffic from the ones that merely look untidy, we can help. Our digital marketing team can then turn the visibility you gain into measurable growth.