Custom Domain

A custom domain for short links — sometimes called a branded domain — is a web address you own that you use as the front of your short URLs. Instead of nimble.li/sale, you share go.acme.com/sale. Same redirect, but the address looks like part of your brand.

A coffee chain called Acme Coffee might set up acme.coffee as a custom domain and share acme.coffee/loyalty on every paper cup. Same destination as a default short URL would reach, but recipients see a domain that matches the brand they're already holding.

Why custom domains exist

The short-link space spent its first decade dominated by free, public shorteners. Phishing campaigns adopted them. Spam filters downgraded them. Email clients flagged them. Recipients learned that "I can't tell where this URL goes" was a reason to be cautious.

The fix was for legitimate publishers to put short links on their own domains. Same redirect technology; different signals to the recipient.

What recipients actually see

The URL you publish reaches people through previews you don't fully control — SMS apps, email clients, hover tooltips, link unfurlers on social platforms. What those previews show is what your link is, in the recipient's eyes.

What recipients actually see

Default short-link domain

nimble.li/sale

A shared shortener domain. Recipients can't tell who's behind the link without clicking.

Custom branded domain

go.acme.com/sale

A subdomain you own. Recipients see your brand in the SMS preview, the hover tooltip, and the address bar.

Same destination, same redirect mechanism. Only the host that recipients (and spam filters) see changes.

Signals the URL itself sends

Beyond the host, recipients (and the spam filters in front of them) weigh a handful of smaller signals when they decide whether to click. None of these is decisive on its own, but they compound.

Signals the URL itself sends

Default short URL

https://nimble.li/7g2k

✓
HTTPS
Encrypted connection.
•
Shared shortener host
Recipients can't tell which brand the link belongs to until they click.
•
Auto-generated slug
/7g2k doesn't communicate what the link is about.
✓
Compact length
Fits cleanly in SMS, ads, and printed materials.

Custom + vanity

https://go.acme.com/sale

✓
HTTPS
Encrypted connection.
✓
Branded host
Subdomain on the publisher's own domain — instantly attributable.
✓
Vanity slug
/sale is human-readable and sayable.
✓
Compact length
Fits cleanly in SMS, ads, and printed materials.

Recipients and spam filters weigh these signals together — no single one is decisive, but a URL that hits most of them lands in inboxes more reliably than one that doesn't.

How a custom domain is wired up

Setting up a custom short-link domain is mostly a one-time DNS step. At your registrar, you add two records on the subdomain — say, go.acme.com:

An A record pointing at the IP your short-link service gives you.
A TXT record with a verification token, so the service can confirm you own the domain.

Once both records propagate, the service flips the domain on. Visitors hitting go.acme.com/... arrive at the service, which handles the redirect.

HTTPS is usually handled for you — most services issue and auto-renew the certificate once the domain is verified.

Apex vs subdomain

It's common to use a subdomain — go.acme.com, link.acme.com — rather than the apex (acme.com). Most teams already run their main website on the apex, and pointing it at a shortener would conflict. If the domain is dedicated to short links, the apex is fine.

Common choices:

go.acme.com — the most common pattern. Generic, neutral.
link.acme.com — descriptive, slightly longer.
acme.link or acm.io — a separate, shorter domain altogether. Less brand recognition, but the URLs are as compact as you can get.

A separate two- or three-letter domain (acm.io) is a bigger commitment but produces the shortest possible URLs — worth the cost if you publish at high volume.

Custom domain vs vanity URL — clarifying the terms

These are independent properties of the same link:

	Default domain	Custom domain
Random slug	`nimble.li/7g2k`	`go.acme.com/7g2k`
Vanity slug	`nimble.li/spring-sale`	`go.acme.com/spring-sale`

A vanity URL is about the slug. A custom domain is about the host. They're independent — but the combination is what produces the strongest signal.