It's a way of generating a valid URL, generally using data already obtained. For instance, using the title of an article to generate a URL. I'd advise to generate the slug, using a function, given a title (or other piece of data), rather than setting it manually.
<title> The 46 Year Old Virgin </title> <content> A silly comedy movie </content> <slug> the-46-year-old-virgin </slug>
Now let's pretend that we have a Django model such as:
class Article(models.Model): title = models.CharField(max_length=100) content = models.TextField(max_length=1000) slug = models.SlugField(max_length=40)
How would you reference this object with a URL, with a meaningful name? You could use Article.id so the URL would look like this:
Or, you could reference the title like so:
www.example.com/article/The 46 Year Old Virgin
Problem is, spaces aren't valid in URLs, they need to be replaced by
%20 which is ugly, making it the following:
That's not solving our meaningful URL. Wouldn't this be better:
That's a slug.
the-46-year-old-virgin. All letters are downcased and spaces are replaced by hyphens
-. See the URL of this very webpage for an example!
If I may provide some historical context :
The term "slug" has to do with casting metal—lead, in this case—out of which the press fonts were made. Every paper then had its fonts factory regularly re-melted and recast in fresh molds, since after many prints they became worn out. Apprentices like me started their career there, and went all the way to the top (not anymore).
Typographs had to compose the text of an article in a backward manner with lead characters stacked in a wise. So at printing time the letters would be straight on the paper. All typographs could read the newspaper mirrored as fast as the printed one. Therefore the slugs, (like snails) also the slow stories (the last to be fixed) were many on the bench waiting, solely identified by their fist letters, mostly the whole title generally more readable. Some "hot" news were waiting there on the bench, for possible last minute correction, (Evening paper) before last assembly and definitive printing.
Django emerged from the offices of the Lawrence journal in Kansas. Where probably some printing jargon still lingers. A-django-enthusiast-&-friendly-old-slug-boy-from-France.