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

**URL:** <https://community.thunkable.com/t/api-works-in-browser-but-doesn-t-trigger-via-thunkable-button/4088043>\
**Category:** Questions about Thunkable X\
**Created:** [August 15, 2025, 1:53pm UTC](https://community.thunkable.com/t/api-works-in-browser-but-doesn-t-trigger-via-thunkable-button/4088043 "2025-08-15T13:53:50Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![leandrocst912zaf4d](https://avatars.discourse-cdn.com/v4/letter/l/35a633/32.png) [@leandrocst912zaf4d](https://community.thunkable.com/u/leandrocst912zaf4d)\
**Post date:** [August 15, 2025, 1:53pm UTC](https://community.thunkable.com/t/api-works-in-browser-but-doesn-t-trigger-via-thunkable-button/4088043/1 "2025-08-15T13:53:50Z")

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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:

 ![image](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/0/9/0908dcde12a9521b1340bb3b095b87c8a71fa716.png)

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!

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<div class="post-metadata">

**Author:** ![matt\_conroy](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/matt_conroy/32/150843_2.png) [@matt\_conroy](https://community.thunkable.com/u/matt_conroy)\
**Post date:** [August 15, 2025, 2:09pm UTC](https://community.thunkable.com/t/api-works-in-browser-but-doesn-t-trigger-via-thunkable-button/4088043/2 "2025-08-15T14:09:45Z")

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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.

 ![Screenshot 2025-08-15 at 10.09.30 AM](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/7/6/769fde64388031b102c7aca1f4bc48254a10a187.png)

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

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**Author:** ![system](https://us1.discourse-cdn.com/flex015/uploads/thunkable/original/3X/0/f/0f59f292712368bce16ff80133ae10de8a6f27e8.png) [@system](https://community.thunkable.com/u/system)\
**Post date:** [November 13, 2025, 2:09pm UTC](https://community.thunkable.com/t/api-works-in-browser-but-doesn-t-trigger-via-thunkable-button/4088043/3 "2025-11-13T14:09:45Z")

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