pip install Flask-HTAuth==0.1.2

Easy to integrate basic HTTP authentication for Flask apps

Source
Among fairly niche packages on PyPI.
Over 625 downloads in the last 90 days.

Commonly used with Flask-HTAuth

Based on how often these packages appear together in public requirements.txt files on GitHub.

Flask-fillin

A flask extension that provides utilities to test forms.

django-queued-storage

Queued remote storage for Django.

Flask-Turbolinks

Turbolinks for Flask.

PyHAML

Pythonic implementation of HAML, cross compiling to Mako template syntax.

Flask-Uploads

Flexible and efficient upload handling for Flask

Flask-Celery-Helper

Celery support for Flask without breaking PyCharm inspections.

WTForms-ParsleyJS

Generate client side, parsley.js validation attributes automatically from WTForms server side validators.

Flask-DjangoQuery

Django like query for Flask-SQLAlchemy

SQLAlchemy-ORM-tree

An implementation for SQLAlchemy-based applications of the nested-sets/modified-pre-order-tree-traversal technique for storing hierarchical data in a relational database.

douban-client

Python client library for Douban APIs (OAuth 2.0)

Flask-Exceptional

Adds Exceptional support to Flask applications

SQLAlchemy-Defaults

Smart SQLAlchemy defaults for lazy guys, like me.

lda

Topic modeling with latent Dirichlet allocation

Flask-Simon

Simple MongoDB Models for Flask

pyspotlight

Python interface to the DBpedia Spotlight REST API

Flask-Principal

Identity management for flask

Flask-Security

Simple security for Flask apps.

pyzipcode

query zip codes and location data

Flask-Selfdoc

Documentation generator for flask

Version usage of Flask-HTAuth

Proportion of downloaded versions in the last 3 months (only versions over 1%).

0.1.2

37.28%

0.1.1

31.36%

0.1

31.36%