Application not picking up .css file (flask/python)


I am rendering a template, that I am attempting to style with an external style sheet. File structure is as follows.

        - mainpage.html
        - mainpage.css

mainpage.html looks like this

        <link rel= "stylesheet" type= "text/css" href= "../styles/mainpage.css">
        <!-- content --> 

None of my styles are being applied though. Does it have something to do with the fact that the html is a template I am rendering? The python looks like this.

return render_template("mainpage.html", variables..)

I know this much is working, because I am still able to render the template. However, when I tried to move my styling code from a “style” block within the html’s “head” tag to an external file, all the styling went away, leaving a bare html page. Anyone see any errors with my file structure?

Asked By: Zack



I’m pretty sure it’s similar to Laravel template, this is how I did mine.

<link rel="stylesheet" href="/folder/stylesheets/stylesheet.css" />

CSS file pathing problem

Simple flask application that reads its content from a .html file. External style sheet being blocked?

Answered By: nCore

In jinja2 templates (which flask uses), use

href="{{ url_for('static', filename='mainpage.css')}}"

The static files are usually in the static folder, though, unless configured otherwise.

Answered By: njzk2

You need to have a ‘static’ folder setup (for css/js files) unless you specifically override it during Flask initialization. I am assuming you did not override it.

Your directory structure for css should be like:

        - mainpage.html
            - mainpage.css

Notice that your /styles directory should be under /static

Then, do this

<link rel= "stylesheet" type= "text/css" href= "{{ url_for('static',filename='styles/mainpage.css') }}">

Flask will now look for the css file under static/styles/mainpage.css

Answered By: codegeek

I’m running version 1.0.2 of flask right now.
The above file structures did not work for me, but I found one that did, which are as follows:

     app_folder/ static/ style.css/ templates/

(Please note that ‘static’ and ‘templates’ are folders, which should be named exactly the same thing.)

To check what version of flask you are running, you should open Python in terminal and type the following accordingly:

import flask

flask –version

Answered By: Ly-Bach

I have read multiple threads and none of them fixed the issue that people are describing and I have experienced too.

I have even tried to move away from conda and use pip, to upgrade to python 3.7, i have tried all coding proposed and none of them fixed.

And here is why (the problem):

by default python/flask search the static and the template in a folder structure like:


you can verify by yourself using the debugger on Pycharm (or anything else) and check the values on the app (app = Flask(name)) and search for teamplate_folder and static_folder

in order to fix this, you have to specify the values when creating the app something like this:

TEMPLATE_DIR = os.path.abspath('../templates')
STATIC_DIR = os.path.abspath('../static')

# app = Flask(__name__) # to make the app run without any
app = Flask(__name__, template_folder=TEMPLATE_DIR, static_folder=STATIC_DIR)

the path TEMPLATE_DIR and STATIC_DIR depend on where the file app is located. in my case, see the picture, it was located within a folder under src.

you can change the template and static folders as you wish and register on the app = Flask…

In truth, I have started experiencing the problem when messing around with folder and at times worked at times not. this fixes the problem once and for all

the html code looks like this:

<link href="{{ url_for('static', filename='libraries/css/bootstrap.css') }}" rel="stylesheet" type="text/css" >

This the code

Here the structure of the folders

Answered By: Stefano Tuveri

The flask project structure is different. As you mentioned in question the project structure is the same but the only problem is wit the styles folder. Styles folder must come within the static folder.

Answered By: Gopi P

Still having problems after following the solution provided by codegeek:
<link rel= "stylesheet" type= "text/css" href= "{{ url_for('static',filename='styles/mainpage.css') }}"> ?

In Google Chrome pressing the reload button (F5) will not reload the static files. If you have followed the accepted solution but still don’t see the changes you have made to CSS, then press ctrl + shift + R to ignore cached files and reload the static files.

In Firefox pressing the reload button appears to reload the static files.

In Edge pressing the refresh button does not reload the static file. Pressing ctrl + shift + R is supposed to ignore cached files and reload the static files. However this does not work on my computer.

Answered By: Christian Johansen

One more point to add on to this thread.

If you add an underscore in your .css file name, then it wouldn’t work.

Answered By: SW Jeong

One more point to add.Along with above upvoted answers, please make sure the below line is added to file:

app = Flask(__name__, static_folder="your path to static")

Otherwise flask will not be able to detect static folder.

Answered By: Sanjay Nandakumar

If any of the above method is not working and your code is perfect then try hard refreshing by pressing ( Ctrl + F5 )for windows and for mac ( hold down Cmd and Shift and then press R [Command + Shift + R ]). It will clear all the caches and then reload file. It worked for me.

Answered By: Hackytech

Add the following to your code:-

 <link rel= "stylesheet" type= "text/css" href= "{{ url_for('static',filename='name of css file') }}">

if you have linked your css like above and its not working then you can do the following:-

  1. Chrome => ctrl + shift + R
  2. Edge => ctrl + shift + R
  3. Firefox => ctrl + shift + R
Answered By: Loop Assembly

Weirdly, for me having a "static" folder along with naming my .css file as "main.css" works. If I have any other filename – for instance "styles.css" or "mainstyle.css" the style is not reflected on the page when it renders.

Answered By: Archit K

If you want to connect the html and css when you are using Blueprints within Flask:

  1. Make sure you have the templates and static folder set:
    core = Blueprint(‘core’, name, template_folder=’templates’, static_folder=’static’)

  2. add the url_for in your href code:

Answered By: Tompis14
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