python-flask.md

Python - Flask example for SameSite=None; Secure

Once the fix to this issue is released, you will be able to use set_cookie() like this:

from flask import Flask, make_response

app = Flask(__name__)

@app.route('/')
def hello_world():
    resp = make_response('Hello, World!')
    # Set a same-site cookie for first-party contexts
    resp.set_cookie('cookie1', 'value1', samesite='Lax')
    # Set a cross-site cookie for third-party contexts
    resp.set_cookie('cookie2', 'value2', samesite='None', secure=True)
    return resp

While you're waiting for the release, you can still set the header explicitly:

from flask import Flask, make_response

app = Flask(__name__)

@app.route('/')
def hello_world():
    resp = make_response('Hello, World!')
    # Set a same-site cookie for first-party contexts
    resp.set_cookie('cookie1', 'value1', samesite='Lax')
    # Ensure you use "add" to not overwrite existing cookie headers
    # Set a cross-site cookie for third-party contexts
    resp.headers.add('Set-Cookie','cookie2=value2; SameSite=None; Secure')
    return resp