Every web page has an address, and the most human-readable part of that address is the slug. You’ve seen thousands of them without knowing the name — it’s the what-is-a-url-slug at the end of this page’s URL. A good slug helps people and search engines understand what a page is about before they even open it. A bad one — ?p=12932 or /page-2-final-v3 — tells nobody anything. Here’s exactly what a slug is, why it matters, and how to write one that’s clean, clear, and SEO-friendly.
What a URL slug actually is
A slug is the part of a URL that comes after the domain (and any folders) and identifies the specific page. Break a URL into its parts:
https://prosetool.com/blog/what-is-a-url-slug/
\_____/ \__________/ \___/\________________/
protocol domain path slug
In https://prosetool.com/blog/what-is-a-url-slug/, the slug is what-is-a-url-slug. It’s the unique, readable label for that page within its section. The word comes from newspaper publishing, where a “slug” was the short name editors used to refer to a story in progress.
| URL | Slug |
|---|---|
| example.com/blog/how-to-bake-bread/ | how-to-bake-bread |
| shop.com/products/blue-running-shoes/ | blue-running-shoes |
| site.com/about/ | about |
Why URL slugs matter
A slug looks like a tiny detail, but it pulls real weight:
- It’s a ranking signal. Google uses words in the URL to understand a page’s topic. A keyword in the slug is a small but genuine relevance cue.
- It affects click-through. Slugs show in the search results, right under the title. A clean, descriptive slug (
/best-running-shoes/) inspires more confidence than a cryptic one (/cat?id=88&ref=2). - It’s shareable. People paste URLs into messages, emails, and social posts. A readable slug tells the recipient what they’re about to click. A string of numbers tells them nothing.
- It’s a usability cue. Readers and crawlers alike use the slug to predict the page content and where it sits in the site.
In short: the slug is free SEO and UX real estate. Wasting it on ?p=12932 leaves value on the table.
What makes a good URL slug
A strong slug follows a handful of consistent rules:
1. Keep it short and descriptive
Use the fewest words that clearly describe the page. /url-slug-guide/ beats /the-complete-and-comprehensive-guide-to-understanding-url-slugs/. Shorter slugs are easier to read, share, and remember — and they rarely get truncated. For the length question specifically, the rule of thumb is “as short as possible while still descriptive.”
2. Include your target keyword
Put the page’s main keyword in the slug, near the front. A post targeting “url slug” should live at /url-slug/ or /what-is-a-url-slug/, not /post-47/. This reinforces the topic for search engines — without crossing into keyword stuffing, which applies to URLs too.
3. Use hyphens, not underscores or spaces
Separate words with hyphens (-). Google explicitly treats hyphens as word separators and underscores as joiners, so blue_shoes reads as one word to a crawler while blue-shoes reads as two. Spaces aren’t allowed in URLs at all — they get encoded as ugly %20 sequences.
4. Use lowercase only
Some servers treat /About/ and /about/ as two different pages, which can split your ranking signals or create duplicate content. Lowercase everything to be safe.
5. Drop stop words and filler
Small words like a, the, and, of, and to usually add nothing to a slug. /how-to-write-a-good-slug/ can become /write-good-slug/ or /good-url-slug/. Trim them unless removing one changes the meaning.
6. Avoid dates and volatile details
A slug like /2024-sale/ ages instantly. Keep slugs evergreen so the URL stays valid even as you update the content — you don’t want to choose between an outdated URL and a risky redirect later.
A quick before-and-after
| Bad slug | Why it’s bad | Better slug |
|---|---|---|
/p?id=4821 | No keywords, unreadable | /url-slug-guide/ |
/The_Best_SEO_Tips_2023/ | Caps, underscores, a date | /seo-tips/ |
/click-here-now/ | No topic, no keyword | /free-trial/ |
/how-to-do-it/ | Vague, no keyword | /how-to-write-a-slug/ |
The fastest way to create a clean slug
You don’t have to format slugs by hand. Type or paste your title into the slug generator and it produces a clean, lowercase, hyphenated slug — stripping accents, symbols, and stray punctuation automatically, with the option to drop stop words. It’s the simplest way to turn “How to Write a Good URL Slug!” into how-to-write-a-good-url-slug in one click.
A couple of related tools pair well with slug work:
- The case converter is handy if you need to normalize a title’s capitalization first.
- The URL encoder/decoder helps when you’re dealing with the rest of a URL’s query string, not just the slug.
Slugs are one piece of a bigger picture
Getting the slug right is one habit among several that make a URL work for SEO — structure, length, readability, and consistency all matter. We pull them together in how to create SEO-friendly URLs. And because the slug shows in search results alongside your title and description, it pays to get all three right at once: see the ideal title tag length and the ideal meta description length.
The bottom line
A URL slug is the readable part of a web address that identifies a specific page — the what-is-a-url-slug at the end of this one. A good slug is short, lowercase, hyphen-separated, keyword-rich, and free of stop words and dates. It helps your page rank, earns more clicks, and travels well when shared. Generate clean ones automatically with the slug generator.
Frequently Asked Questions
What is a URL slug?
A URL slug is the part of a web address that identifies a specific page in a readable way — for example, what-is-a-url-slug in prosetool.com/blog/what-is-a-url-slug/. It’s the unique, human-friendly label for that page within its section of the site.
Do URL slugs affect SEO?
Yes, modestly. Google uses words in the URL to understand a page’s topic, so a keyword in the slug is a small relevance signal. Clean, descriptive slugs also improve click-through from search results and are easier to share.
Should I use hyphens or underscores in a slug?
Use hyphens. Google treats hyphens as word separators but underscores as word joiners, so blue-shoes is read as two words while blue_shoes is read as one. Hyphens are the SEO-safe choice.
How long should a URL slug be?
As short as possible while still clearly describing the page — usually a few words. Short slugs are easier to read, share, and remember, and they’re less likely to be truncated in search results. Drop stop words and filler to tighten them.
How do I create a URL slug?
Take your page title, make it lowercase, replace spaces with hyphens, remove punctuation and accents, and drop unnecessary stop words. The slug generator does all of this automatically in one click.
Can I change a URL slug after publishing?
You can, but if the page already gets traffic or has links, set up a 301 redirect from the old slug to the new one to preserve rankings and avoid broken links. Choosing an evergreen slug up front avoids the need.