## 11.1. Finding Extensions¶

Flask extensions are listed on the Flask Extension Registry and can be downloaded with easy_install or pip. If you add a Flask extension as dependency to your requirements.txt or setup.py file they are usually installed with a simple command or when your application installs.

## 11.2. Using Extensions¶

Extensions typically have documentation that goes along that shows how to use it. There are no general rules in how extensions are supposed to behave but they are imported from common locations. If you have an extension called Flask-Foo or Foo-Flask it should be always importable from flask_foo:

import flask_foo


## 11.3. Building Extensions¶

If you are using Flask 0.7 or earlier the flask.ext package will not exist, instead you have to import from flaskext.foo or flask_foo depending on how the extension is distributed. If you want to develop an application that supports Flask 0.7 or earlier you should still import from the flask.ext package. We provide you with a compatibility module that provides this package for older versions of Flask. You can download it from GitHub: flaskext_compat.py
import flaskext_compat

Once the flaskext_compat module is activated the flask.ext will exist and you can start importing from there.