Reload Flask app when template file changes

Using the latest version of Flask on Windows, using the run command and debug set to true; Flask doesn’t need to be reset for changes to templates to be brought in to effect. Try Shift+F5 (or Shift plus the reload button) to make sure nothing it being cached.

you can use

TEMPLATES_AUTO_RELOAD = True

From http://flask.pocoo.org/docs/1.0/config/

Whether to check for modifications of the template source and reload it automatically. By default the value is None which means that Flask checks original file only in debug mode.

Actually for me TEMPLATES_AUTO_RELOAD = True does not work (0.12 version). I use jinja2 and what i have done:

1. Create function before_request

   def before_request():
       app.jinja_env.cache = {}
   

2. Register it in application

   app.before_request(before_request)
   

3. That’s it.

What worked for me is just adding this:

@app.before_request
def before_request():
    # When you import jinja2 macros, they get cached which is annoying for local
    # development, so wipe the cache every request.
    if 'localhost' in request.host_url or '0.0.0.0' in request.host_url:
        app.jinja_env.cache = {}

(taken from @dikkini’s answer)

When you are working with jinja templates, you need to set some parameters. In my case with python3, I solved it with the following code:

if __name__ == '__main__':
    app.jinja_env.auto_reload = True
    app.config['TEMPLATES_AUTO_RELOAD'] = True
    app.run(debug=True, host='0.0.0.0')

See http://flask.pocoo.org/docs/1.0/quickstart/
and use FLASK_ENV=development

You need to set a TEMPLATES_AUTO_RELOAD property as True in your app config:

from flask import Flask

app = Flask(__name__)
app.config["TEMPLATES_AUTO_RELOAD"] = True

See more on http://flask.pocoo.org/docs/1.0/config/

Updated as of March 2021:

The flask CLI is recommended over app.run() for running a dev server, so if we want to use the CLI then the accepted solution can’t be used.

In Flask 1.1 or later, the environment variable FLASK_RUN_EXTRA_FILES or the option --extra-files effectively do the same thing as the accepted answer. See also this github issue.

Example usage:

flask run --extra-files "app/templates/index.html"
# or
export FLASK_RUN_EXTRA_FILES="app/templates/index.html"
flask run

in Linux. To specify multiple extra files, separate file paths with colons., e.g.

export FLASK_RUN_EXTRA_FILES="app/templates/index.html:app/templates/other.html"

Whole directories are also supported:

flask run --extra-files app/templates/

Templates are reloaded automatically, why not doing ctrl+f5 to refresh the webpage,
cause web-browsers usually save cache.

To reload the application on the server AND in the browser I used the livereload package. Installed through the CLI with

$ pip install livereload

and running the code

from flask import Flask, render_template

app = Flask(__name__)

@app.route("/")
def hello():
    return render_template("index.html")

if __name__ == '__main__':
    from livereload import Server
    server = Server(app.wsgi_app)
    server.serve(host = '0.0.0.0',port=5000)

all answers here using the extra_files argument or TEMPLATES_AUTO_RELOAD config work to reload it on the server but for a smooth development experience without damaging your keyboard’s F5 key I’d go with livereload

I had the same trouble. The solution is really simple though. Instead of this:

if __name__ == '__main__':
    app.jinja_env.auto_reload = True
    app.config["TEMPLATES_AUTO_RELOAD"] = True
    app.run(debug=True)

Put

app.jinja_env.auto_reload = True
app.config["TEMPLATES_AUTO_RELOAD"] = True

above the main function. So final output for example:

from flask import Flask, app,render_template

app= Flask(__name__)
app.jinja_env.auto_reload = True
app.config["TEMPLATES_AUTO_RELOAD"] = True

@app.route('/')
def index():
    return render_template('index.html')

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

Adding app.config['TEMPLATES_AUTO_RELOAD'] = True after if __name__ == '__main__': doesn’t work for me!

What works is adding app.config['TEMPLATES_AUTO_RELOAD'] = True after app = Flask(__name__)

Notice that I am using app.run(debug=True)