The web's case
kebab-case lowercases everything and joins words with hyphens: my-great-article. It is the convention for URLs, filenames, CSS classes and custom HTML attributes. The name comes from the skewer: words threaded on a stick.
Why Google prefers the hyphen
It is documented and unambiguous: Google treats the hyphen as a word separator and the underscore as a joiner. A URL like running_shoes reads as one word, while running-shoes reads as two. That is why kebab-case won in URLs.
Frequently asked questions
Why not kebab-case in code?
Because the hyphen is the subtraction operator: my-variable would be read as «my minus variable». Use snake_case or camelCase in code.
Does it matter for SEO?
Yes, moderately. A readable URL helps Google understand the topic and improves click-through, since the URL is shown in results.
What happens to accented letters?
They are preserved. For a URL you should then replace them — our slug generator handles that.