How to Create SEO-Friendly URL Slugs: Rules, Examples, and Common Mistakes

The URL you publish a page at is one of the few things you set once and then live with for a long time. Change it later and you break every link that pointed to the old address - unless you set up redirects, which takes extra work and still leaves gaps. Get it right the first time and you avoid that problem entirely. The piece of the URL that identifies a specific page is called the slug, and there are concrete rules for writing one well.

What a URL Slug Is (and Why It Matters)

The slug is the last section of a URL, the part that comes after the domain and any subdirectory. In the URL https://example.com/blog/how-to-bake-sourdough/, the slug is how-to-bake-sourdough. It identifies the specific page within that section of the site.

Slugs matter for three reasons. First, they tell search engines what the page is about. A URL like /p=4491 gives a crawler nothing to work with. A URL like /how-to-bake-sourdough/ contains the exact keywords someone might search for, which is one signal among many that affects ranking.

Second, slugs affect click-through rate. When a URL appears in search results or gets shared as a link, people read it. A clean, descriptive slug builds trust. A long, parameter-stuffed URL makes people hesitate before they click.

Third, a good slug is durable. It does not include the date, the author name, or a category that might change. A slug that describes the content rather than metadata around it stays accurate for years without needing to be updated.

The Six Rules for a Well-Formed Slug

There is no single official standard for URL slugs, but best practice has converged on a clear set of rules that web developers and SEO guides consistently agree on.

1. Use lowercase only

Servers treat uppercase and lowercase characters differently. The URLs /Sourdough-Bread/ and /sourdough-bread/ can point to different pages, or to the same page depending on server configuration. Lowercase slugs remove that ambiguity entirely. Some servers will silently redirect uppercase to lowercase; others will serve two separate pages and create a duplicate content problem for search engines. Lowercase is always the safe choice.

2. Use hyphens to separate words

A slug like howtobakedsourdough is technically valid but unreadable. how-to-bake-sourdough is immediately clear to both readers and search engines. Use one hyphen between each word with no leading or trailing hyphens.

3. Remove stop words when they add no meaning

Words like "a", "the", "and", "or", and "in" bulk up a slug without adding keyword value. how-to-bake-sourdough is stronger than how-to-bake-a-sourdough-loaf-in-your-oven because it keeps only the words that identify what the page is actually about. That said, keep stop words if removing them makes the slug ambiguous or genuinely hard to read.

4. Keep it short

Research into click-through rates consistently shows that shorter URLs perform better. Aim for three to five meaningful words. A slug like how-to-bake-sourdough is stronger than complete-beginner-guide-how-to-bake-sourdough-bread-at-home-from-scratch. Shorter slugs are also easier to share verbally and less likely to get cut off in social media previews.

5. Strip special characters

Parentheses, ampersands, question marks, apostrophes, and similar characters create URL encoding problems. The apostrophe in "baker's" becomes %27 in a URL, making the address harder to read and share. Remove them from slugs entirely. If a character is not a letter, a number, or a hyphen, it should not be in your slug.

6. Never include dates or version numbers

A slug like sourdough-recipe-2024 is already misleading if the page gets updated in 2026. The page becomes harder to maintain, and if you ever want to move away from the date you have to either live with an inaccurate URL or migrate it and set up a redirect. Describe the content, not when it was written.

Hyphens vs Underscores: Why the Difference Still Matters

For most of the web's history, underscores and hyphens were treated differently by search engine crawlers. Google has confirmed that it treats hyphens as word separators and underscores as word connectors. That means sourdough-bread is parsed as two words - "sourdough" and "bread" - while sourdough_bread is treated as a single compound word, "sourdouhbread".

In practice, this means a slug with underscores is less likely to rank for searches that use the individual words separately. Hyphens are unambiguous: every major search engine, every browser, and every accessibility tool reads them as word breaks.

If you have old content with underscores in the URLs, the cleaner approach is to replace them with hyphens rather than leaving them in place. This also applies to filenames you might turn into slugs - underscores in a filename that gets used as a page path carry the same SEO penalty.

Special Characters, Accents, and Symbols

Characters outside the basic Latin alphabet cause problems in URLs. An accented character like the "e" in "resume" with an accent must be percent-encoded as %C3%A9 to appear in a URL, which makes the address long and unreadable. Most CMS platforms convert accented characters automatically, but the result is not always consistent across different systems and browsers.

The reliable approach is to convert accented and special characters to their plain ASCII equivalents before publishing. "Resume" works cleanly as a slug. The percent-encoded version of an accented slug is noise.

Em dashes are another common source of slug problems. They appear frequently in headlines and article titles, and writers sometimes paste titles directly into slug fields without checking. An em dash in a slug becomes %E2%80%94, which is meaningless noise in a URL and looks broken when shared as a link.

Other characters to remove before creating a slug: colons, semicolons, quotation marks (both straight and curly), exclamation points, question marks, parentheses, brackets, slashes, and the hash symbol. The hash character is especially problematic because browsers use it for anchor links - anything after a hash never reaches the server, so a slug with a hash character will silently truncate.

Cleaning Up Old Slugs Without Breaking Links

Most sites accumulate poorly formed URLs over time. An early CMS setup that appended dates, a plugin that added numeric IDs, or a bulk import that preserved underscores from original filenames - these issues compound and are worth cleaning up deliberately.

The right way to fix a slug is to clean it up and then set a 301 redirect from the old URL to the new one. A 301 is a permanent redirect that tells search engines the page has moved. Most of the link equity the old URL had accumulated transfers to the new address, and any external links that pointed to the old URL will continue to work.

The process works like this: build a spreadsheet of old URLs and their new equivalents, set up the redirects in your server config or CMS redirect manager, then update any internal links that still point to the old addresses. The internal link update is the step most people skip, which means their own pages continue to send visitors through a redirect chain rather than linking directly to the correct URL.

Finding and updating internal links is the tedious part. A find-and-replace operation across your site content can catch most of them quickly. Find and Replace Text lets you paste in a block of content and replace every instance of an old URL with the new one - useful for checking page content before publishing the redirect.

One caution: do not redirect old URLs to unrelated pages. Redirecting every broken URL to the homepage might seem like a safe fallback, but search engines eventually recognize this pattern as a soft 404 and stop treating it as a valid redirect. Match each old URL to the most relevant live page, and if there is no relevant page, let the old URL return a real 404 rather than faking a redirect.

How to Slugify Text in Seconds

Writing a slug by hand from a long headline is tedious and easy to get wrong. The manual steps are: lowercase everything, strip special characters, convert spaces to hyphens, remove stop words where needed, and verify the result reads clearly. Doing that for every piece of content you publish is slow and inconsistent.

A slug generator handles all of this automatically. Paste in the full title of your post or page and the tool returns a URL-ready slug: lowercase, hyphenated, and stripped of characters that would cause problems in a browser.

This matters most in high-volume publishing environments. If you write a few articles a week, manually formatting slugs is a minor annoyance. If you publish dozens of product pages or posts per week, the time savings add up quickly. More importantly, the consistency improves: automated slugs follow the same rules every time, which means your URL patterns stay predictable and your site is easier to audit later when you want to check for patterns or fix bulk issues.

Summary

A URL slug is worth getting right the first time because fixing it later requires redirects, internal link updates, and careful tracking to avoid broken pages. The core rules are straightforward: lowercase only, hyphens between words, no special characters, remove stop words that add nothing, and never include dates or version numbers. Hyphens beat underscores because search engines parse them as word separators. Em dashes and accented characters should be stripped before any title becomes a slug. When old slugs need fixing, 301 redirects preserve link equity and a find-and-replace pass handles internal links. And for consistent, error-free slugs at any publishing volume, a slug generator is faster and more reliable than doing it by hand.