I created a React app using Strapi for backend and I don’t understand how to setup CORS policy.
Strapi is on my online server, and I run React app on my local computer. When I tried to send a request with Axios, there is this problem :
Access to XMLHttpRequest at ‘http address’ from origin ‘http://localhost:3000’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: No ‘Access-Control-Allow-Origin’ header is present on the requested resource.
You shouldn’t need this as allowing * is the current default. Generally CORs issues like this come from the frontend sending improper request headers in which Strapi will only respond with what it can support.
If the request headers don’t match the response headers then frontend stacks will generally throw an error like you are seeing. We will need to do know what you are sending to help.
Can you please double check that your app got restarted after the modifications to CORS settings?
Can you open the developer tools in your browser and look at the Network tab when you request your backend from the frontend. The browser should make an OPTIONS request to check if your request is allowed:
Thank you for all your answers, it enlightened me on how Strapi works. I found the solution: it was a simple mistake on my part in the ReactJS part. Indeed, I used the wrong port (80 instead of 1337). I solved this problem yesterday. Thank you! I took the opportunity to use the right version of NodeJS, and listen to everything you said.
Indeed on my firefox it works fine. The problem is when I try to connect from my phone once the app is compile and run on it.
I am using node v14.15.3. Strapi 3.4.1 installed step by step using strapi documentation.
The only thing I maintain is the API folder.
Anyway, this is the code on my front-end Ionic:
That is a good observation. I don’t know how to see the requesting from the device. The code works perfectly from my localhost requesting to my virtual server. Once, on a minor version (<3.0.0) of strapi I could configurate the server and the client, using config/enviroment/… folders and JSON config archives. But, this is not working anymore. I upgrade strapi and configurated middleware.js, but it is not work.
I checked my connection from my device to the server via ping. But, when I tried to access to the server using postboy from the mobile, I obtained an error.
private server = 'http://192.168.0.50'; private port = '1337';
That way, I construct my address for login to strapi.
I know there is an issue connecting from webview that makes different the origin and strapi looks that like a different source. But, I couldn’t find the solution…
I didn’t know the format of forlders is still being used.
I will put brackets  on the origin but I tried that before.
How can I see webview console of my device?
How do I know middleware.js is running on my strapi server?
Irdk, that’s not a thing related to Strapi, so I would suggest to google it, there you will find more information on how to debug mobile browser. As I remember there is a thing in Developer tools where you active USB debugging and on your phone you should also activate USB debugging. Then you connect the phone through USB to your PC and it will detect it in the browser. Something like that.
You can run the app in console mode: yarn strapi console, now you can execute real-time commands inside the server, type the following command: strapi.middleware, it will return an object with all the middlewares:
Thanks a lot pal…I didn’t solve the problem but now I have almost a confirmation. I realize a couple of things.
One, the device is sending correctly the request:
Accept: application/json, text/plain, /
Content-Type: application/json; charset=UTF-8
User-Agent: Mozilla/5.0 (Linux; Android 9; Redmi Note 6 Pro Build/PKQ1.180904.001; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/87.0.4280.101 Mobile Safari/537.36
Two, the strapi server is refusing the request:
Failed to load the response data
And finally, Strapi is not loading my configuration via middleware.js:
Sorry pal, I recently look your answer. I am not on my computer now.
I am working in ionic and I am using Cordova http installed on capacitor. I know that it is used for web browsers but it is supposed that works with the right strapi cors configuration.
The other way is hardest one. I will have to reprogram all my code making two services. One for browser and other for devices using advanced-native-http and use condition to select one or the other depending on platform.
Or, to use only native-advanced-http and ionic proxy.
Both ways are hard. I have working we promises and I will have to refactor all my code in order to use observables.