Build a Simple URL Shortener in Python — No Framework Required!

Ever wondered how Bitly or TinyURL shortens long links into just a few characters? In this post, we’ll build a fully functional URL shortener using pure Python — no Flask, no Django, just the standard library + a tiny storage system.

Perfect for learning about:

• Hashing and encoding

• Dictionaries as in-memory databases

• Basic URL redirection logic

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🎯 What We’ll Build

plaintextCopyEditLong URL ➡️ "https://openai.com/research/gpt-4o"
Short Code ➡️ "k1Dz2A"

You store and retrieve links like:
  shorten("https://...") → "k1Dz2A"
  expand("k1Dz2A") → "https://..."

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🧱 Step 1: Set Up the Code Structure

Create a file url_shortener.py:

pythonCopyEditimport hashlib
import base64

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🔧 Step 2: Encode URLs

Use SHA-256 and Base64 to create short but unique codes:

pythonCopyEditdef shorten_url(long_url):
    hash_object = hashlib.sha256(long_url.encode())
    b64_encoded = base64.urlsafe_b64encode(hash_object.digest())
    short_code = b64_encoded[:6].decode()  # 6-char short code
    return short_code

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💾 Step 3: Save and Retrieve Mappings

pythonCopyEdit# In-memory database (use pickle or JSON to persist if needed)
url_map = {}

def store_url(long_url):
    short_code = shorten_url(long_url)
    url_map[short_code] = long_url
    return short_code

def retrieve_url(short_code):
    return url_map.get(short_code, "Not found")

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✅ Step 4: Try It Out

pythonCopyEditif __name__ == "__main__":
    long = input("Enter a long URL: ")
    code = store_url(long)
    print("Shortened Code:", code)

    recovered = retrieve_url(code)
    print("Original URL:", recovered)

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🧪 Sample Run

bashCopyEditEnter a long URL: https://openai.com/research/gpt-4o
Shortened Code: 1d8a9F
Original URL: https://openai.com/research/gpt-4o

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🛠 Bonus: Make It a Command-Line Tool

bashCopyEditpython url_shortener.py shorten "https://example.com"
python url_shortener.py expand "k1Dz2A"

Use argparse to add this easily (see CLI blog post!).

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📡 Want to Go Further?

• Add a Flask or FastAPI interface

• Store mappings in a real DB like SQLite

• Add expiration for links

• Track number of clicks