Build Your Own URL Shortener

Building a URL shortener is a classic project that many software developers tackle, mainly because it starts as a simple API but can quickly become complex when you need to scale it. In fact, designing a URL shortener is a common interview question since it challenges developers to think about functionality and scalability.

How URL Shortening Works

1. Take a long URL as input.
2. Generate a short, unique key for the URL.
3. Store the original URL and key in a database.
4. When users visit the short URL, redirect them to the original URL.

Here is a Javascript Example

const express = require('express');
const app = express();
const port = 3000;

app.use(express.json()); // Middleware to parse JSON requests

// In-memory database to store URLs for demonstration purposes
const urlDatabase = {};

// Function to generate a short code
function generateShortCode() {
return Math.random().toString(36).substr(2, 6); // Generates a 6-character code
}

// Endpoint to shorten a URL
app.post('/shorten', (req, res) => {
const originalUrl = req.body.url;

// Generate a unique short code
let shortCode = generateShortCode();

// Ensure unique code by regenerating if it already exists
while (urlDatabase[shortCode]) {
shortCode = generateShortCode();
}

// Store the original URL with the short code
urlDatabase[shortCode] = originalUrl;

// Send back the shortened URL
res.json({ shortUrl: `http://localhost:${port}/${shortCode}` });
});

// Endpoint to redirect from the short URL to the original URL
app.get('/:shortCode', (req, res) => {
const shortCode = req.params.shortCode;

// Look up the short code in the database
const originalUrl = urlDatabase[shortCode];

if (originalUrl) {
// Redirect to the original URL
res.redirect(originalUrl);
} else {
// Send an error if the short code is not found
res.status(404).json({ error: "URL not found" });
}
});

// Start the server
app.listen(port, () => {
console.log(`URL shortener service listening at http://localhost:${port}`);
});

Here is a PHP Example

<?php
// Connect to SQLite database
$db = new PDO('sqlite:url_shortener.db');

// Function to generate a unique short code
function generateShortCode($length = 6) {
return substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), 0, $length);
}

// Function to shorten a URL
function shortenURL($originalUrl) {
global $db;

// Generate a unique short code
do {
$shortCode = generateShortCode();
$stmt = $db->prepare("SELECT COUNT(*) FROM urls WHERE short_code = ?");
$stmt->execute([$shortCode]);
$exists = $stmt->fetchColumn() > 0;
} while ($exists);

// Insert the original URL and short code into the database
$stmt = $db->prepare("INSERT INTO urls (original_url, short_code) VALUES (?, ?)");
$stmt->execute([$originalUrl, $shortCode]);

// Return the full shortened URL
return "http://localhost/shortener.php?code=$shortCode";
}

// Function to redirect to the original URL
function redirectToOriginalURL($shortCode) {
global $db;

// Look up the original URL by short code
$stmt = $db->prepare("SELECT original_url FROM urls WHERE short_code = ?");
$stmt->execute([$shortCode]);
$originalUrl = $stmt->fetchColumn();

if ($originalUrl) {
// Redirect to the original URL
header("Location: $originalUrl");
exit();
} else {
// Return an error if the short code is not found
echo "Error: URL not found.";
}
}

// Main Logic
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
// Handle shortening a URL
$originalUrl = $_POST['url'];
if (filter_var($originalUrl, FILTER_VALIDATE_URL)) {
$shortUrl = shortenURL($originalUrl);
echo "Shortened URL: <a href='$shortUrl'>$shortUrl</a>";
} else {
echo "Invalid URL provided.";
}
} elseif (isset($_GET['code'])) {
// Handle redirecting based on short code
$shortCode = $_GET['code'];
redirectToOriginalURL($shortCode);
} else {
// Display a form to shorten a URL
echo '<form method="POST">
<label for="url">Enter URL to shorten:</label>
<input type="text" name="url" id="url" required>
<button type="submit">Shorten URL</button>
</form>';
}
?>

Why Choose T.LY Instead?

While building your URL shortener can be fun and educational for most businesses and users, T.LY is a practical, cost-effective, and reliable choice. It handles all the complex aspects of URL management, leaving you to focus on growing your audience and sharing content without technical hassle.