Build Your Own URL Shortener API

The "URL Shortener API" project involves developing an API that allows users to shorten long URLs into shorter, easily shareable links. The API will accept a long URL, generate a shortened version, and return the shortened link. Additionally, the API will handle redirects from the short URL to the original long URL. The API should also support optional features such as link expiration, analytics tracking (e.g., number of clicks), and custom aliases for shortened URLs. The goal is to provide a scalable, fast, and easy-to-use API that can be integrated into web or mobile applications for shortening and managing URLs.

Detailed Description

URL shortening services are widely used to make long URLs more manageable, especially for sharing on social media, messaging apps, and other platforms with character limits. This API will allow developers to easily shorten long URLs by generating short links that redirect to the original URL. The service will also support advanced features like setting expiration dates for links, tracking click statistics, and creating custom short link aliases.

Example Usage

A user has a long URL like https://www.example.com/articles/2024/09/how-to-use-url-shortener. They can submit this URL to the API, which will return a shortened URL like https://short.ly/abcd1234. When users visit https://short.ly/abcd1234, they will be redirected to the original long URL. Optionally, the user can customize the short link (e.g., https://short.ly/awesome-article), set expiration dates, and view analytics on link usage.

Introduction
Objectives
Functional Requirements
Non-Functional Requirements
Use Cases
User Stories
Technical Requirements
API Endpoints
Security
Performance
Documentation
Glossary
Appendix

1. Introduction

The "URL Shortener API" will provide users with the ability to shorten long URLs and redirect visitors from shortened links to the original long URLs. The API will also offer optional features like link expiration, custom short link aliases, and analytics tracking. It will be designed to handle high volumes of requests with fast response times and ease of use.

2. Objectives

Allow users to input a long URL and receive a shortened version.
Redirect users from the shortened URL to the original long URL.
Provide optional features such as custom aliases, link expiration, and click tracking.
Ensure the API is scalable, fast, and secure.

3. Functional Requirements

URL Shortening

Shorten URL: Accept a long URL as input and return a shortened URL.
Custom Aliases: Allow users to create custom aliases (e.g., short.ly/my-link) instead of using a random string.
Link Expiration: Allow users to set an expiration date after which the short link will no longer work.

URL Redirection

Redirect Short URL: When a user visits the short URL, redirect them to the original long URL.
404 for Invalid Links: Return a 404 error for invalid or expired short links.

Analytics (Optional)

Track Clicks: Track the number of clicks or visits for each short URL.
Analytics Dashboard: Provide an endpoint for users to view analytics, including click counts and geographic data.

Optional Features

Password Protection: Allow users to protect their short links with a password.
Batch URL Shortening: Enable users to shorten multiple URLs in a single request.
QR Code Generation: Provide a QR code for each shortened URL.

4. Non-Functional Requirements

Scalability: The API should handle a large number of requests and grow with increasing user demand.
Performance: The API should generate shortened URLs and handle redirects with minimal latency.
Security: Ensure that short links are secure and prevent malicious use of the API (e.g., phishing or spam).
Reliability: The API should maintain high uptime and consistent performance, especially for redirection.

5. Use Cases

Shorten a URL: A user inputs a long URL, and the API returns a shortened version.
Redirect from Short URL: A user visits the short URL, and the API redirects them to the original long URL.
View Analytics: A user views the number of clicks or visits their shortened link has received.
Set Expiration: A user creates a short link that automatically expires after a set period (e.g., 7 days).

6. User Stories

As a user, I want to shorten a long URL so that I can share it easily.
As a user, I want to create custom aliases for my short links so they are easy to remember.
As a user, I want to track how many people have clicked on my short link so that I can measure its effectiveness.
As a user, I want to set an expiration date for my short links so that they become invalid after a certain period.
As a developer, I want to integrate a URL shortening service into my application for generating short, shareable links.

7. Technical Requirements

Programming Language: Use a backend language like Node.js, Python, or Ruby.
Framework: Use Express.js (Node.js), Flask (Python), or Rails (Ruby) for routing and API logic.
Database: Use a relational or NoSQL database (e.g., PostgreSQL, MongoDB) to store URLs, analytics, and expiration data.
Unique Identifier Generation: Use a hash function or ID generation library to create unique shortened URLs.
Caching: Implement caching for frequently accessed short URLs to improve redirect performance.

8. API Endpoints

Shorten URL

Endpoint: POST /api/shorten
Request Body:
```
json
```
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{ "url": "https://www.example.com/articles/2024/09/how-to-use-url-shortener", "custom_alias": "awesome-link", "expiration_date": "2024-10-01" }
Response:
```
json
```
Copy code
{ "short_url": "https://short.ly/awesome-link", "original_url": "https://www.example.com/articles/2024/09/how-to-use-url-shortener", "expiration_date": "2024-10-01" }

Redirect from Short URL

Endpoint: GET /{short_url}
Response: 302 Redirect to original URL or 404 if the short URL is invalid or expired.

View Analytics (Optional)

Endpoint: GET /api/analytics/{short_url}
Response:
```
json
```
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{ "short_url": "https://short.ly/awesome-link", "original_url": "https://www.example.com/articles/2024/09/how-to-use-url-shortener", "clicks": 150, "last_click": "2024-09-24", "geography": { "US": 100, "UK": 25, "IN": 25 } }

Delete/Expire Short URL

Endpoint: DELETE /api/shorten/{short_url}
Response:
```
json
```
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{ "message": "Short URL deleted successfully" }

9. Security

HTTPS: Ensure all data transmission is encrypted using HTTPS.
Rate Limiting: Implement rate limiting to prevent abuse or spamming of the URL shortening service.
Validation: Validate input URLs to prevent users from shortening malicious or harmful URLs.
Blacklist Malicious Domains: Use a blacklist to prevent known malicious domains from being shortened.

10. Performance

Caching: Cache frequently accessed short URLs for faster redirects.
Database Indexing: Ensure the database is indexed by short URL to speed up lookups during redirection.
CDN Integration: Use a Content Delivery Network (CDN) to serve short URLs globally for faster access.

11. Documentation

Provide API documentation using tools like Swagger to make it easy for developers to integrate the URL Shortener API.
Include examples of requests, responses, error messages, and how to handle optional features like custom aliases and expiration.

12. Glossary

URL: Uniform Resource Locator, the address used to access a resource on the internet.
Redirect: Sending users from one URL to another (e.g., from a shortened URL to the original long URL).
Alias: A custom, human-readable identifier for a shortened URL (e.g., awesome-link instead of a random string).
302 Redirect: An HTTP status code indicating that the requested resource has been temporarily moved to a different URL.

13. Appendix

Include flowcharts or diagrams showing the lifecycle of URL shortening and redirection.

Let me know if you need further modifications or additional details!