Using underscores in URLs might seem like a minor detail, but it can lead to several practical and technical problems that affect website usability, SEO, and link sharing. This list covers key issues with underscores in URLs for web developers, SEO specialists, and content creators who want to optimize their sites for both search engines and users.
Underscores Are Treated Differently by Search Engines
Google and other major search engines interpret underscores (_) differently than hyphens (-). While hyphens are recognized as word separators, underscores are not; Google treats words connected by underscores as a single word. This can negatively impact keyword recognition and ranking because search engines struggle to parse the individual words within the URL.
Users Find Underscores Harder to Read or Recognize
When URLs are shared in text or verbally, underscores can be easily missed or confused with spaces, especially because underscores sit at the baseline and are less visible. This leads to user frustration and errors when typing or copying URLs, reducing click-through rates and accessibility.
Underscores Are Not Easily Clickable in Hyperlinks
Some browsers and email clients underline links, but the underscore character is often hidden under this underline, making it difficult for users to distinguish it from the underline itself. This can cause confusion about whether the underscore is part of the URL or just formatting, leading to broken links if users try to type them manually.
Legacy Web Servers May Handle Underscores Poorly
Certain older web servers and content management systems have issues parsing URLs with underscores, sometimes interpreting the underscore as a special character or causing routing errors. While this is less common today, it can still affect websites running on legacy infrastructure or custom URL rewriting rules.
Underscores Can Complicate URL Canonicalization
URL canonicalization is critical for SEO to avoid duplicate content penalties. Because underscores are treated as part of a word, URLs with and without underscores may not be recognized as duplicates or variants, causing search engines to index multiple versions of the same page and dilute ranking signals.
Social Media Platforms May Parse Underscores Incorrectly
When URLs with underscores are shared on social media, some platforms truncate or misinterpret them, especially in auto-linking contexts. This can lead to broken links or reduced visibility of shared content, negatively affecting social media marketing efforts.
Underscores Are Less SEO-Friendly Compared to Hyphens
SEO best practices recommend hyphens for word separation because search engines parse them clearly as delimiters. Using underscores instead can reduce keyword relevance in URLs, limiting SEO performance and organic search traffic over time.
Accessibility Tools Struggle with Underscores
Screen readers and other accessibility tools may read URLs with underscores awkwardly or skip over them, making navigation difficult for users relying on assistive technology. This undermines web accessibility standards and can exclude users with disabilities.
Underscores Can Cause Confusion in Analytics and Tracking
Some analytics platforms and URL tracking tools treat underscores inconsistently, which can lead to misattribution of traffic or fragmented reporting. This complicates data analysis and makes it harder to measure the performance of specific pages or campaigns accurately.
Replacing or Changing Underscores Later Is Problematic
If a site initially uses underscores and later switches to hyphens, it requires extensive 301 redirects and URL updates. This is time-consuming and risks losing link equity, causing temporary drops in search rankings and user confusion during the transition period.
How to Choose
When deciding whether to use underscores or hyphens in URLs, the most important factors are SEO clarity, user readability, and technical compatibility. Hyphens are widely recommended because they clearly separate words for search engines and users alike, improving keyword relevance and link usability. Underscores, while technically valid, introduce ambiguities and potential issues that outweigh any minor aesthetic preference. Ultimately, consistency across your site and adherence to SEO best practices should guide your choice.
Frequently Asked Questions
Are underscores in URLs bad for SEO? Yes, because search engines treat underscores as word joiners, which can reduce keyword recognition and negatively impact SEO.
Can I use underscores in URLs if I prefer them? Technically yes, but it’s not recommended due to readability, SEO, and technical issues. Hyphens are the safer choice.
Do all search engines treat underscores the same way? Most major search engines, including Google and Bing, treat underscores as word joiners, but minor variations might exist with less common search engines.
Will using underscores break my links? Not inherently, but users may misread or mistype URLs with underscores, leading to broken links or lost traffic.
Is it possible to fix URLs with underscores without hurting SEO? Yes, but it requires careful 301 redirects and updating all internal and external links to preserve link equity.
Can underscores affect social media sharing? Yes, some social platforms may truncate or misinterpret underscores, causing broken or incomplete links in posts.
Final Thoughts
While underscores in URLs are valid and sometimes unavoidable, their drawbacks in terms of SEO, user experience, and technical compatibility make them a less-than-ideal choice for most websites. Hyphens are the preferred standard for separating words in URLs because they improve search engine parsing, readability, and link sharing. For anyone building or maintaining a website, understanding these issues can help avoid common pitfalls and ensure URLs contribute positively to site performance and user engagement.
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