Hyphens vs Underscores in URL Slugs: Which Is Better for SEO?
Use hyphens. Google explicitly treats hyphens as word separators, meaning /seo-tips-for-beginners is read as four distinct words. Underscores, by contrast, join words together - so /seo_tips_for_beginners is interpreted as one single token: seo_tips_for_beginners.
Google's John Mueller confirmed this directly: hyphens are the recommended separator for URL slugs because they help Googlebot understand the individual keywords within your slug, which supports better keyword matching and relevance signals.
In practice, the difference is easy to apply:
- ✅
/best-url-slug-practices- readable, keyword-separated, Google-friendly - ❌
/best_url_slug_practices- treated as one unbroken string by Google
This is a small formatting choice that costs nothing to get right and can quietly improve how your pages rank for the exact terms your slug contains. For related guidance, see 10 Best Brand Keyword Monitoring Tools For B2b Saas Founders.
How Long Should a URL Slug Be?
Keep your URL slug between 3 and 5 words, ideally under 60 characters. Shorter slugs are easier to read, share, and index.
Search engines truncate long URLs in results pages, which can bury your target keyword. Concise slugs also reduce the risk of keyword dilution - every word carries more weight when there are fewer of them.
Compare these two examples:
- ❌
/blog/here-are-some-useful-seo-tips-for-complete-beginners-in-2024 - ✅
/blog/seo-tips-for-beginners
The shorter slug is cleaner, keyword-focused, and far more shareable. If your page title is long, strip stop words like and, the, and for to trim the slug without losing meaning. For related guidance, see Why AI Engines Hallucinate Brand Facts In 2026 And How To Stop It.
What Happens to SEO When You Change a URL Slug?
Changing a live URL slug without a 301 redirect will cost you ranking equity - often permanently.
When you alter a slug, search engines treat the new URL as a completely fresh page. Any backlinks pointing to the old address stop passing authority, and Google must re-crawl and re-index the new URL from scratch. That process typically takes two to eight weeks, during which your page may drop out of the SERPs entirely.
For example, if you rename /blog/seo-tips-for-beginners to /blog/seo-beginner-guide, every external site linking to the old URL now hits a dead end unless you set up a 301 redirect. That single redirect preserves roughly 90–99% of the original link equity.
Before changing any slug, run through this checklist: For related guidance, see Setup Your Site On Google Search Console.
- Set up a 301 redirect from the old URL to the new one immediately.
- Update all internal links across your site to point to the new slug.
- Submit the new URL via Google Search Console to accelerate re-indexing.
- Monitor rankings and crawl errors for at least 30 days post-change.
Common URL Slug Mistakes to Avoid
Even small slug errors can quietly damage your rankings and confuse users before they ever reach your page.
One of the most common mistakes is including dates in slugs. A URL like /blog/2021/06/seo-tips becomes outdated instantly - if you update the content, the date contradicts the freshness, and changing the slug means managing redirects. Keep slugs timeless: /blog/seo-tips works in any year.
Keyword stuffing is another trap. A slug like /best-seo-tips-top-seo-advice-seo-guide-2024 looks spammy to both Google and real users. Use one clear target phrase and stop there.
Here are four more mistakes worth avoiding:
- Uppercase letters -
/SEO-Tipsand/seo-tipscan register as two separate URLs, creating duplicate content - Special characters - symbols like
&,%, or#break readability and can cause crawl errors - Underscores instead of hyphens - Google treats underscores as joiners, so
seo_tipsreads as one word, not two - Excessively long slugs - anything beyond four to five words adds noise without SEO benefit
Getting these details right is just as important as following best practices from the start.