Webmaster & Network·4 min read

How Short Links Work: Redirects, QR Codes, Link Rot

Behind every short link is a tiny lookup table: a slug on one side, your long URL on the other, and an HTTP redirect stitching them together. That's genuinely all there is to how short links work, yet that small mechanism carries QR campaigns, print ads, SMS blasts, and every character-limited bio field on the internet. It also introduces a brand new failure mode, because the link only lives as long as the table does. This article covers the mechanics, the print use case, and the downsides nobody puts on the landing page.

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How short links work: one slug, one redirect

A database row wearing a URL costume.

When you shorten an address, the service generates a compact slug, stores slug plus destination in a database, and hands you a URL on its own domain. When someone opens that URL, the server looks up the slug and answers with a redirect status and a Location header pointing at your original address. The visitor's browser follows it automatically; total added delay is usually a few dozen milliseconds.

Everything else a shortener might offer, click counting, branded domains, expiring links, is decoration on that lookup. Which is why the trust question always reduces to one thing: who controls the table your link depends on?

When shortening a URL actually earns its keep

Some destinations are unspeakable.

The strongest case is anywhere a human transcribes the address: radio spots, podcasts, conference slides, business cards, billboards. Nobody types a 90-character path with three query parameters off a poster, but a short domain plus five characters survives the trip from eyeball to keyboard.

The second case is space budgets. SMS messages, social bios, and printed tables of contents all punish length. The third is tidiness in front of an audience: a slide that says one clean link reads better than a wrapped URL spanning two lines. If none of those apply, and the link lives in an email or a webpage where it's clickable anyway, shortening adds a dependency without adding value.

A worked example: 84 characters down to a scannable link

From query-string soup to poster-ready.

Input: https://example.com/spring-sale?utm_source=poster&utm_medium=print&utm_campaign=q3, which is 84 characters of unspeakable tracking soup. Output: a link on this site's domain around 30 characters long that resolves in a single redirect hop to that exact address, with a QR code drawn beside it ready to scan.

The important detail is order of operations. The UTM parameters went in before shortening, so every scan and click still lands with full campaign attribution. The destination is frozen at creation time, so decorating the long URL afterward isn't possible; get the tracking right first, then compress.

Short links in print and QR campaigns

Ink is unforgiving.

Print is where short links stop being cosmetic and become functional. A QR code's density grows with the length of the text it encodes, so a compact URL yields a coarser, more forgiving pattern that scans reliably from a wobbling phone at an odd angle. Shorten first, then encode, and the same physical size of code becomes measurably easier to read.

The URL Shortener here draws a 200 pixel code automatically, which is fine for screens and quick tests. Before a real print run, generate the code at higher resolution, print a proof at final size, and scan it under bad lighting from arm's length. Every failed scan in the wild is a customer you paid to almost reach.

Link rot risks every shortened URL carries

Your link now has two ways to die.

A normal URL breaks when the destination moves. A shortened one also breaks when the shortener does, and that's not hypothetical: when Google wound down goo.gl, years of links in published papers, tweets, and printed books stopped resolving. Link rot risks compound with time horizon, so the longer the artifact lives, the more that middle dependency costs.

There's also an honesty dimension. Many free third-party shorteners monetize by logging every click, and some insert ad interstitials between reader and destination. A self-hosted link, like the ones made here, redirects straight to the address you entered with nothing bolted on, but the general rule stands: know whose infrastructure sits between your audience and your content.

URL shortening mistakes that break campaigns

The failures below are all avoidable, and all common:

Shortening before adding tracking. The destination can't be edited later, so a forgotten utm_campaign is forgotten forever.
Printing without a live test. Always open the short link and scan the QR code end to end before anything goes to the printer.
Keeping no record of the mapping. Maintain a simple sheet of short link, destination, and where it was published, or future you will be decoding slugs blind.
Using shortened links where trust matters. Password resets and invoices behind an opaque slug read as phishing to cautious recipients.

URL Shortener next to QR Code Generator and UTM Builder

These three tools chain naturally. Start with the UTM Builder to attach source, medium, and campaign to your long URL, so analytics can tell the poster apart from the newsletter. Then shorten the tagged address here. If the destination is print, finish with the QR Code Generator to produce a high resolution code of the short link sized for the actual artwork.

Going the other direction, the URL Expander reverses the trick: paste any short address and see its full redirect chain and true destination. It's the natural way to verify your own links behave exactly as intended.