Flask-Minify

0.50 verified Fri May 01 auth: no python

Flask extension that automatically minifies HTML, CSS, JS and Less responses using various minifiers. Current version 0.50, released April 2025. Active development, roughly quarterly releases.

pip install flask-minify

Common errors

error AttributeError: module 'flask_minify' has no attribute 'Minify' ↓

cause Old version (pre-0.39) used a different import pattern; or a stale cached .pyc.

fix

Upgrade to latest: pip install --upgrade flask-minify. Also clear __pycache__ if needed.

error ImportError: cannot import name 'minify_response' from 'flask_minify' ↓

cause The decorator was moved to the main module in 0.50. Old imports from flask_minify.decorators break.

fix

Use 'from flask_minify import minify_response' for version >=0.50.

error TypeError: Minify() got an unexpected keyword argument 'dash' ↓

cause The 'dash' parameter was removed in version 0.49.

fix

Remove the 'dash' argument from Minify() call. It is no longer supported.

error pip install flask-minify fails with error: legacy-install-failure (or similar) ↓

cause Missing build dependencies or incompatible Python version (e.g., Python 3.7 before 0.49).

fix

Upgrade Python to >=3.8; install wheel: pip install wheel; then retry.

Warnings

breaking In version 0.49, support for Python 3.7 was dropped and the dash option (--dash) was removed. Upgrade Python to 3.8+. ↓

fix Use Python >=3.8; remove any usage of the 'dash' parameter.

deprecated The `htmlmin` backend is unmaintained; the library switched to a fork in 0.43. Using htmlmin may cause compatibility issues in the future. ↓

fix Use the default backend or install tdewolff-minify (pip install flask-minify[tdewolff]) for better support.

gotcha If you install only the base package, minification of CSS/JS may silently fail because cssmin/jsmin are optional dependencies. The extension will still serve the original content without error. ↓

fix Install with extras: pip install flask-minify[htmlmin] or pip install flask-minify[tdewolff] to ensure minifiers are available.

gotcha The `minify_response` decorator does not work on class-based views (MethodView). It only works on view functions. ↓

fix Use the global Minify(app=app) initialization for class-based views, or apply the decorator manually inside the method's return.

gotcha Less compilation is only triggered if the response has a .less extension. If you serve Less files with a wrong Content-Type, it won't compile. ↓

fix Ensure your route returns files with .less extension, or override the Content-Type header to text/less.

Install

pip install flask-minify[htmlmin]

pip install flask-minify[tdewolff]

Imports

Minify
```
from flask_minify import Minify
```
Main class to initialize the extension.
decorators
wrong
```
from flask_minify.decorators import minify_response
```
correct
```
from flask_minify import minify_response
```
In versions >=0.50, the decorator is imported directly from flask_minify. The old path may still work but is not guaranteed.

Quickstart

Initialize Minify with the Flask app. By default, only HTML is minified if no arguments are passed. Explicitly enable CSS/JS.

from flask import Flask
from flask_minify import Minify

app = Flask(__name__)
Minify(app=app, html=True, css=True, js=True)

@app.route('/')
def index():
    return '<html><body><h1>Hello</h1></body></html>'

if __name__ == '__main__':
    app.run()