🔐 Design a TinyURL System (Like Bit.ly) — From Scratch
Ever wondered how Bit.ly shrinks huge URLs into tiny ones like https://bit.ly/abc123?
In this article, you’ll build your own TinyURL system step-by-step — and learn some system design + algorithmic magic along the way.
✅ Problem Statement
Design a URL shortening service. It should:
Convert a long URL into a short one
Retrieve the original long URL from the short one
Be scalable and efficient
🧠 The Idea
We’ll map long URLs to short codes like this:
https://www.example.com/very/long/url
→ https://tinyurl.com/abc123
Behind the scenes:
Use a base62 encoding (a-zA-Z0-9) for compact URLs
Store mappings in a HashMap
Optionally store data in a database for persistence
🔢 Base62 Encoding
To make URLs short, we encode integers in base62:
Base62 characters = [a-z, A-Z, 0-9] = 26 + 26 + 10 = 62 chars
We can assign each long URL a unique ID (like 123456), and convert that number into a base62 string.
💻 Code (Python Example)
Step 1: Base62 Encoder
import string
class TinyURL:
def __init__(self):
self.url_to_code = {}
self.code_to_url = {}
self.counter = 1
self.alphabet = string.ascii_letters + string.digits
def encode_base62(self, num):
base = 62
chars = []
while num > 0:
num, rem = divmod(num, base)
chars.append(self.alphabet[rem])
return ''.join(reversed(chars)).rjust(6, '0') # pad to 6 characters
def encode(self, long_url):
if long_url in self.url_to_code:
code = self.url_to_code[long_url]
else:
code = self.encode_base62(self.counter)
self.url_to_code[long_url] = code
self.code_to_url[code] = long_url
self.counter += 1
return f"https://tinyurl.com/{code}"
def decode(self, short_url):
code = short_url.split("/")[-1]
return self.code_to_url.get(code, "URL not found")
🔄 Usage Example
tiny = TinyURL()
short = tiny.encode("https://www.example.com/article/how-to-make-a-url-shortener")
print("Short URL:", short)
original = tiny.decode(short)
print("Original URL:", original)
⚙️ Behind the Scenes
The counter ensures every new URL gets a unique number.
encode_base62 makes that number small & URL-safe.
Two hash maps store mappings for quick lookup (O(1)).
🔐 Optional Add-ons
Add expiration time to short URLs.
Limit number of requests per user (rate limiting).
Use a database like Redis/PostgreSQL for real storage.
Generate random codes instead of using counters.
🚀 Real-World Scenarios
This technique is used in:
Bit.ly
Twitter link shortener (t.co)
WhatsApp preview links
Firebase Dynamic Links
👨💻 Final Thoughts
“You just built your own Bit.ly system from scratch!
It’s a blend of system design, data structures, and algorithmic creativity.”
Let me know if you want the JavaScript / Java / C++ version too!
🖊️ Written by Raj Guru Yadav
📌 Teen developer & builder of 700+ projects
