How URL Shorteners Work and How to Build One

How URL Shorteners Work and How to Build One

URL shorteners are services that take long URLs and generate shorter, more compact URLs. These shorter URLs redirect users to the original long URL when they are accessed. The primary purpose of URL shorteners is to make long URLs more manageable, shareable, and memorable.

Here’s a general overview of how URL shorteners work:

Receiving the long URL: When a user submits a long URL to a URL shortener service, the service receives the URL as input.

Generating a unique key: The URL shortener generates a unique identifier or key for the long URL. This key is usually a combination of alphanumeric characters.

Storing the mapping: The shortener service stores the mapping between the generated key and the original long URL in a database or some form of persistent storage. This mapping allows the service to retrieve the original URL when the shortened URL is accessed.

Creating the short URL: The short URL is constructed by appending the generated key to a domain owned by the URL shortener service. For example, if the shortener’s domain is “,” the short URL may look like “”

Redirection: When someone accesses the short URL, the URL shortener service receives the request. It looks up the mapping between the key in the short URL and the original long URL. If a matching mapping is found, the service issues a redirect response (HTTP 301 or 302) to the user’s browser, instructing it to navigate to the original long URL.

To build a URL shortener, you’ll need to implement the following steps:

Set up a web server: You’ll need a web server to handle incoming requests and serve the shortened URLs.

Design a database: Create a database schema to store the mappings between the generated keys and the original long URLs. Commonly used databases for this purpose include MySQL, PostgreSQL, or NoSQL databases like MongoDB.

Create a user interface: Develop a user interface that allows users to submit long URLs and displays the corresponding shortened URLs.

Generate unique keys: Implement a function that generates unique keys for each long URL submitted. You can use algorithms like Base62 encoding or UUIDs to generate these keys.

Store the mapping: When a user submits a long URL, store the generated key and its corresponding long URL in the database.

Handle redirection: Set up a redirect endpoint on your web server that takes the short URL as input, looks up the corresponding long URL in the database, and issues the appropriate redirect response to the user’s browser.

Analytics and statistics (optional): If desired, you can implement analytics to track the number of clicks, referrers, and other relevant statistics for the shortened URLs.

It’s important to consider security measures when building a URL shortener to prevent abuse, such as adding rate limiting, ensuring URLs are valid, and protecting against malicious inputs.

Building a URL shortener involves web development, database management, and server-side programming. Depending on your programming language preferences, you can use frameworks like Flask (Python), Express (Node.js), or Ruby on Rails to build the necessary components.

Remember to take into account scalability considerations if you expect a high volume of traffic, as URL shorteners can be subject to significant load due to the redirection process.