Blueprints let you organize routes into modules.

Instead of one giant app.pyapp.py, you can split features like:

• auth
• blog
• admin
• api

Each module can own:

• routes
• templates
• static files

Mental model

• Flask()Flask() app is the “main application”
• Blueprint()Blueprint() is a reusable, modular set of routes

  flowchart TB
  App[Flask App] --> BP1[auth Blueprint]
  App --> BP2[blog Blueprint]
  App --> BP3[api Blueprint]

Why Blueprints matter

• Keeps routes manageable
• Encourages separation of concerns
• Makes collaboration easier
• Works well with the app factory pattern

A simple blueprint

auth/routes.pyauth/routes.py:

from flask import Blueprint
 
auth_bp = Blueprint("auth", __name__)
 
 
auth_bp.route("/login")(lambda: "login")

from flask import Blueprint
 
auth_bp = Blueprint("auth", __name__)
 
 
auth_bp.route("/login")(lambda: "login")

You still must register the blueprint with the app (next page).