Slug rules, reserved slugs and duplicates

Updated 2026-09-08

Slugs are the part of the link people actually read. Domain settings, Slug generation, controls how automatic ones are made and what a person is allowed to type.

The automatic rule

When you create a link without typing a slug, one is generated using the domain's rule:

  • Incremental — 1, 2, 3 and so on. Short and guessable; only sensible on an internal domain.
  • Random 4 — around 1.7 million combinations.
  • Random 6 — around 2 billion combinations. The default, and the right answer for almost everyone.
  • Random 8, 10 or 12 — longer and progressively harder to enumerate. Use 12 when links point at something that should not be discovered by scanning.

Generation retries on collision, so a busy domain does not fail to create a link.

What a slug may contain

Letters, numbers and the characters . _ ~ - /. A slash is allowed, so go.example.com/docs/api is one link rather than a folder. A global reserved list rejects slugs that would collide with system paths, and you can add your own reserved list per domain — brand names, terms you plan to use later, anything you do not want a colleague claiming by accident.

Case sensitivity

Off by default: /Promo and /promo are the same link. Turning it on doubles your effective namespace and roughly doubles your support tickets, because nobody transcribes capitals correctly from print. Leave it off unless you are importing a case-sensitive namespace from elsewhere.

Duplicate destinations

By default, creating a second link to a destination that already has one is refused with a 409 and the existing link attached, so you can reuse it. That is usually right: near-identical links split your click data for no reason.

Turn Allow duplicate destinations on when your workflow genuinely needs one link per campaign or per channel pointing at the same page — which is a reasonable thing to want, since the UTM values differ even when the destination does not.

AI slug suggestions

With AI slug generation enabled, the create dialog and the editor can propose readable slugs from the destination page, and suggest tags from its content. Suggestions are suggestions: type your own whenever you have a better one.

Find this in your dashboard

  1. Sign in and select the workspace and domain you want to manage.
  2. Open Domains. Review the article’s steps and your plan’s available controls.
  3. Save your changes, reopen the record and verify the saved result. For routing changes, check the short link with a test visit.
ShortFreeURL Domains in a demonstration workspace
Domains · Demo workspace. Click to enlarge.

API workflow guides · Open dashboard

Was this helpful?

Start Free — no credit card

The free plan includes 1,000 links, 6 custom domains and 50,000 tracked clicks a month, free forever. Choose a free subdomain from six shared domains. Paid plans start at $4 a month when you outgrow it, and you keep everything you have built.