How to Set Status Code in Flask: Simple Guide

In Flask, you set the HTTP status code by returning a tuple from your route function with response_body and status_code, like return 'OK', 200. Alternatively, use the make_response() function to create a response object and set its status_code property.

Syntax

There are two common ways to set the status code in Flask:

• Return tuple: Return a tuple with the response body and the status code.
• Response object: Use make_response() to create a response, then set its status_code.

Example syntax:

return <response_body>, <status_code>

response = make_response(<response_body>)
response.status_code = <status_code>
return response

python

return 'Hello, world!', 200

from flask import make_response
response = make_response('Hello, world!')
response.status_code = 200
return response

Example

This example shows a Flask app with two routes: one returns a 200 OK status, the other returns a 404 Not Found status using the tuple method and the make_response method.

python

from flask import Flask, make_response

app = Flask(__name__)

@app.route('/success')
def success():
    return 'Success!', 200

@app.route('/notfound')
def not_found():
    response = make_response('Not Found', 404)
    return response

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

Output

When you visit /success, the browser shows 'Success!' with status code 200.
When you visit /notfound, the browser shows 'Not Found' with status code 404.

Common Pitfalls

Common mistakes when setting status codes in Flask include:

• Returning only the response body without the status code, which defaults to 200.
• Returning the status code as a string instead of an integer.
• Not using make_response when you want to set headers or cookies along with the status code.

Example of wrong and right ways:

python

from flask import Flask
app = Flask(__name__)

@app.route('/wrong')
def wrong():
    # Wrong: status code as string, ignored by Flask
    return 'Error', '404'

@app.route('/right')
def right():
    # Right: status code as integer
    return 'Error', 404

Quick Reference

Method	Usage	Example
Return tuple	Return (body, status_code)	return 'OK', 200
make_response	Create response, set status_code	resp = make_response('OK') resp.status_code = 200 return resp

Key Takeaways

Return a tuple with response body and integer status code to set status in Flask.

Use make_response() to customize response objects including status codes.

Always use integer status codes, not strings.

Default status code is 200 if none is specified.

Setting status code correctly helps browsers and clients understand your response.