Why does my Flask route return a 405 error when I submit a form?

[MatteoMgr2008]

I'm using Flask and trying to handle a form submission with POST, but I keep getting a 405 Method Not Allowed error.

Here's the basic code:

from flask import Flask, request

app = Flask(__name__)

@app.route("/submit")
def submit():
    if request.method == "POST":
        name = request.form["name"]
        return f"Hello, {name}!"
    return "Invalid method"

I submit the form from an HTML page using method="POST", but Flask still returns a 405.

What am I doing wrong?

[ThiefMaster]

Because you need methods=('GET', 'POST') on your route() call to allow POST in addition to GET.

[Istituto-freudinttheprodev]

Great question!

The issue is that your route is only set to accept GET requests by default, since you didn’t specify the allowed methods.

To fix the 405 error, you need to explicitly allow POST in the route definition using the methods parameter:

@app.route("/submit", methods=["GET", "POST"])
def submit():
    if request.method == "POST":
        name = request.form["name"]
        return f"Hello, {name}!"
    return "Invalid method"
This tells Flask to accept both GET and POST requests on that route.

Let me know if it works! ✅

[MatteoMgr2008]

Thank you so much!