What Is a URL Slug and Why It Matters for SEO

A URL slug is the part of a web address that identifies a specific page. In the URL https://uttir.com/blog/what-is-a-slug, the slug is what-is-a-slug. A good slug is short, readable, and tells both humans and search engines what the page is about. This guide covers the rules, the edge cases, and the SEO impact.

What is in a URL?

Most URLs have three parts:

• Protocol — https://
• Domain — uttir.com
• Path — /blog/what-is-a-slug

The path is what identifies the page. It is usually broken into segments separated by /. The last segment (and sometimes earlier ones) is called the slug.

What makes a good slug

Descriptive

The slug should tell a human what the page is about. /blog/how-to-format-markdown is good. /blog/post-12345 is bad — the user (and Google) has no idea what the page contains until they open it.

Short

Aim for 3-6 words. Long slugs are harder to read, harder to share, and easier to mistype. /blog/cidr is too short. /blog/a-complete-guide-to-everything-you-need-to-know-about-cidr-notation-for-ip-networking is too long. /blog/what-is-cidr-notation is right.

Lowercase

Slugs are case-sensitive on most web servers. /Blog/Hello and /blog/hello are different URLs. Most sites force lowercase to avoid this confusion. Pick one case and stick to it. Lowercase is the convention.

Hyphens, not underscores

Use - to separate words, not _. Google treats hyphens as word separators but not underscores. /blog/what-is-cidr is read as four words. /blog/what_is_cidr is read as one word. The underscore trick used to be common (it's how Perl, Python, and C-style languages name things); it is wrong for URLs.

No special characters

ASCII letters, digits, and hyphens. No spaces, no apostrophes, no question marks, no non-English characters. Most web frameworks handle URL encoding automatically, but the displayed slug in the address bar should be plain text.

Stable

Once a slug is published, do not change it. The slug is part of the URL, and the URL is part of how the page is linked, bookmarked, and indexed. Changing the slug breaks every link. If you must change, set up a 301 redirect from the old URL to the new one.

How to generate a slug from a title

The basic algorithm:

1. Lowercase the string.
2. Remove all non-alphanumeric characters except spaces and hyphens.
3. Replace spaces with hyphens.
4. Collapse multiple hyphens into one.
5. Trim leading and trailing hyphens.

For example, "How to Format Markdown — A Visual Cheatsheet" becomes how-to-format-markdown-a-visual-cheatsheet with the basic algorithm. The Uttir Slug Generator runs this in your browser and handles the edge cases that the basic algorithm misses.

The edge cases the basic algorithm misses

Non-ASCII characters

Accented characters, Cyrillic, Greek, CJK, Arabic, Hebrew, and other non-Latin scripts need to be transliterated or removed. "Café au lait" should become cafe-au-lait, not caf-au-lait or caf%C3%A9-au-lait. The right approach: maintain a transliteration table for common characters. é → e, ñ → n, ü → u, etc.

Smart quotes and dashes

Text copied from word processors often contains "smart" quotes (curly) and em-dashes (—). The basic algorithm strips these. The better approach: convert them to their ASCII equivalents first. " → ", — → -.

Amperands and other symbols

"Cats & Dogs" should become cats-and-dogs, not cats-amp-dogs. Ampersand is a common English word; it should be expanded to "and". The same applies to + (plus), @ (at), % (percent).

Numbers

Keep numbers as-is, but be careful with leading zeros and large numbers. "007 James Bond" should be 007-james-bond (preserve the leading zeros) or 7-james-bond (drop them). Most slug generators preserve them. "Version 1.0.0" should be version-1-0-0 (dots become hyphens) or version-1.0.0 (preserve the dots). The latter is more common in technical writing.

Emoji

Strip emoji. They look great in titles, terrible in URLs. "How to use 🚀 in your code" should be how-to-use-in-your-code, not how-to-use-%F0%9F%9A%80-in-your-code.

Truncation

Long slugs should be truncated to a reasonable length (50-75 characters). Truncate at a word boundary, not in the middle of a word. "How to format a long English title that goes on and on" should become how-to-format-a-long-english-title (15 words truncated to 7, cut at a word boundary).

Slugs in different contexts

Blog posts

Most blogs use the post title (or a simplified version) as the slug. The Uttir blog uses slugs like how-to-format-markdown, what-is-cidr-notation, and how-to-read-a-whois-record. Short, descriptive, hyphenated.

Product pages

E-commerce sites often include the product name, category, and sometimes an ID. /shoes/running/nike-pegasus-40 is good. /p/12345 is bad for SEO but acceptable for tracking.

User profiles

Most sites use the username. /@ada or /users/ada. Strip non-URL-safe characters from the username first.

News articles

News sites often include the date. /2026/08/15/breaking-news-story. This is fine for SEO (Google prefers recent content for news queries) but creates a lot of stale URLs when stories are old. A flat /news/breaking-news-story is simpler and more durable.

Slugs and SEO

The SEO impact of slugs is small but real. Google has confirmed that slugs are a minor ranking signal. A page with a descriptive slug (/blog/what-is-cidr-notation) has a slight advantage over a page with a non-descriptive slug (/blog/p=12345) for the same content, all else equal.

The mechanism: the slug is one of the places Google looks for relevance signals. If the slug contains the search term, the page is more likely to be relevant. Combined with the title tag, the H1, and the body content, a descriptive slug is one of several factors that make a page rank for a query.

But the impact is small. A great slug with bad content will not rank. A bad slug with great content might still rank. Do not over-engineer slugs: keep them short, descriptive, and stable. Move on to the content.

Common slug mistakes

Stop words

Some SEO guides recommend removing stop words (a, an, the, of, in) from slugs. "How to choose the right image format" becomes choose-right-image-format. The argument: shorter, more keyword-dense. The counter-argument: harder to read, sometimes ambiguous. The right answer: keep the slug readable. A short stop word is fine.

Keyword stuffing

Do not stuff keywords into the slug. /blog/best-cheap-running-shoes-for-men-2026-review is keyword stuffing. /blog/best-running-shoes-2026 is fine. Google does not reward stuffing and may penalize it.

Date prefixes

/blog/2026/08/15/... makes the page look stale. Date is a fact, not a selling point. Most modern blogs do not include the date in the slug.

Changing the slug

Once a slug is published, it is a public URL. Changing it breaks every link — bookmarks, social shares, search engine indexes, citation in other articles. If you must change, set up a 301 redirect from the old URL to the new one. Do not change slugs for cosmetic reasons.

Trailing slashes

/blog/foo and /blog/foo/ are technically different URLs. Most sites redirect one to the other. Pick one (the convention is no trailing slash for content URLs, trailing slash for directory URLs) and enforce it.

How Uttir generates slugs

The Uttir Slug Generator runs in your browser and handles the edge cases:

• Transliteration for accented characters (café → cafe, naïve → naive)
• Smart quote conversion (" → ")
• Ampersand expansion (& → and)
• Emoji stripping
• Truncation at word boundaries
• Multiple-hyphen collapsing
• Lowercase normalization

Paste a title, get a slug. The full pipeline is 100% client-side.

Bottom line

A good URL slug is short, descriptive, lowercase, and hyphenated. It is a small SEO signal but more importantly, it makes the URL readable and shareable. Generate it once, set it, and never change it. The Uttir Slug Generator handles the edge cases in your browser.