How Short URLs Work - The Magic Trick That Shortens Long Addresses

Why Would You Want to Shorten a URL?

The URL (address) of a website can sometimes become very long. For example, the URL of a product page on Amazon can exceed 100 characters. If you try to send this long URL to a friend, the message becomes hard to read. On SNS there are character limits, so a long URL alone takes up most of a post.

When you store a URL in the black-and-white square pattern, too, the longer the URL, the larger and more complex the pattern becomes. If you are printing it on a business card or flyer, a smaller pattern looks better. For these reasons, "URL shorteners" that make long URLs shorter were born. Well-known examples include bit.ly, t.co (X/Twitter), and goo.gl (Google, now discontinued).

How Short URLs Work - The Magic of "Forwarding"

The way short URLs work is actually very simple. It is the same principle as a postal "forwarding request." When you move house and submit a forwarding request to the post office, letters delivered to your old address are forwarded to your new address, right? Short URLs are the same: when you access a short URL, the server tells you "the real URL is over here" and automatically forwards (redirects) you.

Specifically, when you access bit.ly/abc123, the bit.ly server searches its database to find that "the real URL corresponding to abc123 is https://www.example.com/very/long/path/to/page," and returns an instruction to the browser saying "please go there" (an HTTP 301 redirect). The browser automatically moves to the real URL. This processing is completed in about 0.1 seconds, so users hardly notice it.

The Risks of Short URLs - The Problem of Not Seeing Where a Link Goes

Behind their convenience, short URLs carry risks. The biggest problem is that you cannot tell where a link goes before you click it. Just by looking at bit.ly/abc123, you cannot judge whether it leads to a legitimate site or to a phishing scam site. A malicious person can hide a link to a dangerous site behind a short URL.

As a countermeasure, there are services that let you check the redirect destination in advance if you add a "+" to the end of the short URL (bit.ly/abc123+). Also, some security software has a function that automatically checks where short URLs redirect to. Before clicking a short URL sent by someone you do not know, be sure to check the redirect destination.

What the Dynamic Square Pattern and Short URLs Have in Common

In fact, the way the dynamic square pattern works is almost the same as a short URL. A short URL is stored in the pattern, and when that URL is accessed, the server redirects to the real link destination. The link destination can be changed later because all it takes is rewriting the database on the server side.

Thanks to this mechanism, you can change the link destination of a pattern later, even after it has been printed. Operations such as switching to another page when a campaign ends, or changing the menu for each season, become possible. The pattern itself does not change, yet the content you reach when you scan it changes. This is why it is called "dynamic."

Another Weakness of Short URLs

Besides the problem of not being able to see where they go, short URLs have a weakness that is easy to overlook. It is that when the service providing the shortening disappears, every short URL created with that service loses its function at once. Even if the original long URL is still alive, if the shortening mechanism that calls it up stops, you cannot get anywhere. In exchange for convenience, you are entrusting your destination to the continued existence of an outside service. The more you want to use a link for a long time, the more important it is to choose with awareness of whether the provider will continue stably.

Living Safely With Short URLs

Short URLs are a convenient tool, but both the people who use them and the people who receive them can improve safety with a little care. If you use a mechanism that lets you check the destination in advance before opening a short URL you have received, you can ease the worry of being sent to an unexpected site. When you create a short URL yourself, choosing a trustworthy provider and adding a description that shows where it goes lets the other person open it with peace of mind. Rather than making shortening the only goal, thinking about how to make up for the destination becoming invisible is the knack for getting along well with short URLs.

Try Making a Short URL Yourself

Short URLs can be made easily and for free. Just go to bit.ly and enter the URL you want to shorten. If you create an account, you can also check statistics such as the number of clicks on the short URLs you have created, the countries of the people who clicked, and the devices they used.

However, free URL shorteners come with points to watch out for. When a service ends, every short URL you have created becomes invalid. In fact, Google's goo.gl stopped anonymous use and issuing to new users on April 13, 2018 (existing users could continue using it, including issuing, until March 30, 2019), and the management console also ended on March 30, 2019. Redirects for existing links were maintained after that, and on August 25, 2025, only the links that had no usage record as of the end of 2024 were deactivated (links with a usage record have been maintained since then). In other words, the lifespan of a short URL placed on printed material depends on the issuer's policy, and you cannot control it on your side. For URLs you plan to use for a long period (such as those printed on business cards or signs), we recommend running short URLs on your own domain or choosing a highly reliable service.