API works in browser but doesn’t trigger via Thunkable button

[leandrocst912zaf4d]

Hello!
I’m developing an app in Thunkable that calls a Flask API hosted on PythonAnywhere.
The API works fine — when I access the endpoint directly in the browser (e.g., https://myusername.pythonanywhere.com/classificar), I get the expected JSON response.

However, when I click the button in the app (configured with a Web API Component using the POST method), nothing happens.
Here’s my block flow:

Additional information:

• Method: POST

• API doesn’t require authentication, it just receives data and returns JSON.

• In the browser, the response is OK (status code 200).

• In Thunkable, no error message and no response are shown.

• I’ve tested on both Thunkable Live and web preview.

• URL is correctly set in the Web API component.

My questions:

1. Is there any limitation in Thunkable’s free version that delays or blocks POST requests to external APIs?

2. Do I need to set any extra headers or parameters for the POST to work correctly?

3. Could this issue be related to CORS even when testing in Thunkable Live?

Thanks for your help!

[matt_conroy]

t sounds like you may be running into an issue with Cross-Origin Resource Sharing (CORS). CORS can prevent a web API from working on some devices or browsers.

Could you please test it using the Thunkabke live app or download the app on a mobile device?

This way we can verify that the issue is caused by CORS.

I would also suggest taking advantage of the error handling blocks within Thunkable for testing on your mobile device.

You can find more about CORS information here: https://docs.thunkable.com/blocks/advanced-app-features/web-api/cors-policy