Using underscores (_) in URLs might seem harmless, but for website owners, developers, and SEO professionals, it can cause several issues that impact usability, search engine ranking, and user experience. This listicle explores the main problems with underscores in URLs, explaining why they matter and how they can affect your site’s performance and visibility.
Underscores Are Not Treated as Word Separators by Google
Google’s search algorithm treats underscores as joiners rather than separators. For example, the URL example.com/blue_car and example.com/bluecar are interpreted similarly, meaning “blue_car” is read as a single word “bluecar.” This contrasts with hyphens, which Google interprets as word breaks, helping it better understand keyword relevance. This can negatively affect SEO when targeting multi-word keywords.
Reduced Readability for Users
URLs with underscores are harder for users to read and interpret quickly. When underscores connect words, they tend to blend into the text, especially in underlined links where the underscore can disappear or look like part of the underline. This decreases URL clarity and can make it more difficult for users to share or remember the URL accurately.
Compatibility Issues with Some Browsers and Email Clients
Certain browsers and email clients do not handle underscores well in URLs, especially when links are underlined. The underscore can be mistaken for part of the underline style and become invisible, leading users to misread or misclick the link. This can result in broken links or user frustration, particularly in email marketing campaigns.
Harder to Type and Pronounce
Underscores are less intuitive to type and communicate verbally compared to hyphens. On many keyboards, the underscore requires pressing the Shift key, which slows down typing. Additionally, when sharing URLs verbally, saying “underscore” is less natural and can cause confusion, whereas “dash” or “hyphen” is more straightforward.
Potential Confusion with Programming and File Naming Conventions
Underscores are commonly used in programming languages and file names, which can cause confusion when users see them in URLs. For example, users might mistake underscores in URLs for code or parameters rather than part of the readable path, reducing trust or understanding about the page content.
Underscores Can Affect Analytics Tracking Consistency
In some analytics setups, URLs with underscores might be inconsistently tracked or grouped. Some tools may treat similar URLs with underscores differently from those with hyphens, causing fragmented data. This complicates accurate measurement of traffic and user behavior, especially when URL variations exist.
Underscores Limit URL Structure Flexibility
Using underscores can restrict how URLs are structured or interpreted by some content management systems (CMS) or frameworks. Some CMS platforms automatically convert spaces to hyphens but not underscores, leading to inconsistent URL formats. This necessitates extra configuration or manual adjustments to maintain uniform URL standards.
Less Common and Less Recognizable in URLs
Hyphens are the standard and widely accepted word separator in URLs, making underscores less familiar to most users. This unfamiliarity can lead to mistrust or hesitation before clicking a URL containing underscores, especially among less tech-savvy audiences. Familiar URL structures encourage clicks and sharing.
Search Engines Prefer Hyphens Over Underscores
Though Google recognizes underscores, its guidelines explicitly recommend using hyphens to separate words in URLs. Bing and other search engines also favor hyphens. Ignoring this guidance may put your site at a slight disadvantage in search rankings compared to competitors using hyphens consistently.
Difficulty in Link Sharing on Social Media Platforms
On social media and messaging apps, URLs with underscores might be truncated or rendered incorrectly, especially when combined with automatic hyperlinking and formatting. This can result in broken links or confusion about the correct URL, reducing referral traffic from these channels.
How to Choose
When deciding whether to use underscores or hyphens in URLs, focus primarily on SEO best practices, user experience, and technical compatibility. Hyphens are generally preferred because they improve search engine readability, enhance user clarity, and avoid many display issues across browsers and email clients. While underscores won’t break your URLs, they complicate indexing and sharing. If you inherit URLs with underscores, consider implementing 301 redirects to hyphenated versions for SEO benefits and consistency. Ultimately, choose the format that aligns with your CMS capabilities, branding guidelines, and audience familiarity, but hyphens remain the safest and most effective choice.
Frequently Asked Questions
Can using underscores in URLs hurt SEO?
Yes, because search engines like Google treat underscores as joiners, not word separators, which can reduce keyword relevance and negatively impact SEO.
Are underscores invalid in URLs?
No, underscores are valid characters in URLs, but their use is discouraged for the reasons related to readability and SEO.
Should I change existing URLs with underscores to hyphens?
If possible, yes. Changing underscores to hyphens with proper 301 redirects helps preserve SEO value and improves user experience.
Do other search engines besides Google treat underscores the same way?
Most major search engines, including Bing and Yahoo, prefer hyphens as word separators and treat underscores less favorably.
Is it okay to use underscores in file names but not URLs?
Yes, underscores are common in file names and programming but not recommended in URLs due to the different considerations for web indexing and user experience.
Can URL underscores cause problems in email marketing?
Yes, underscores can disappear in underlined links in emails, causing confusion or broken links, so hyphens are safer for clickable URLs in emails.
Final Thoughts
While underscores are technically allowed in URLs, their use introduces several practical and SEO-related challenges. From search engine indexing quirks to user readability and link sharing issues, underscores can limit your website’s effectiveness and reach. For anyone managing websites or digital content, adopting hyphens as the standard URL word separator is a straightforward way to avoid these pitfalls and ensure better visibility and user engagement. If you currently use underscores, consider transitioning carefully to hyphens with proper redirects to maintain your site’s health and performance.
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