cors | Cross-Origin Resource Sharing for koa | Application Framework library

If this is a local environment, you don't need to configure Spring, instead you modify angular configuration.

Create a file proxy.conf.json in your project's src/ folder.

Add the following content to the new proxy file:

Instead of this:

Below Steps can help to solve issue in chrome 98, for other browser like edge you need to do similar like chrome.

• Requestly with chrome version 98. You need to follow following steps :- Run this command on terminal

  defaults write com.google.Chrome InsecurePrivateNetworkRequestsAllowed -bool true

• Restart your Browser, Not work then restart your machine

• Run 'regedit' to open windows registry (If permission issue came then run that command with Admin command prompt)
• Go to Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome
• Create new DWORD value with "InsecurePrivateNetworkRequestsAllowed" Name
• Change Value to "1"
• Restart your Browser

The reason you're seeing a network request is probably because you're using the Cache-Control: no-cache header in your request.

As seen here:

The no-cache response directive indicates that the response can be stored in caches, but the response must be validated with the origin server before each reuse, even when the cache is disconnected from the origin server.

Cache-Control: no-cache

If you want caches to always check for content updates while reusing stored content, no-cache is the directive to use. It does this by requiring caches to revalidate each request with the origin server.

Note that no-cache does not mean "don't cache". no-cache allows caches to store a response but requires them to revalidate it before reuse. If the sense of "don't cache" that you want is actually "don't store", then no-store is the directive to use.

See here: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control#response_directives

Here is what a full request for a cached asset looks like on my network tab, when the asset returns 304 Not Modified from the validation request. (from S3) This is in a background: url context.

This is because of a root CA Let’s Encrypt uses (and Mongo Atals uses Let's Encrypt) has expired on 2020-09-30 - namely the "IdentTrust DST Root CA X3" one.

The fix is to manually install in the Windows certificate store the "ISRG Root X1" and "ISRG Root X2" root certificates, and the "Let’s Encrypt R3" intermediate one - link to their official site - https://letsencrypt.org/certificates/

Copy from the comments: download the .der field from the 1st category, download, double click and follow the wizard to install it.

The HTML attribute crossorigin defines how to handle crossorigin requests. Setting the crossorigin attribute (equivalent to crossorigin="anonymous") will switch the request to a CORS request using the same-origin policy. It is required on the rel="preload" as font requests require same-origin policy.

The same-origin policy is required on almost all new resource types, such as fetch(),

I just solve this issue by correcting the RxJS version to 7.4.0. I hope this can solve others issue as well.

I don't understand, I need to specify the bearer token somehow, even in the docs it says to put it in the Authorization header, why aren't they allowing it?

This is a different problem, is not related to the Bearer token at all. From the error you're getting, it means, the origin you're using to fetch the Slack API, is not trusted (http://127.0.0.1:5500), there is nothing you can do from the browser since this is a policy that comes from the server which defines the authorized origins. (Learn more about CORS here) Since I don't think this is supported by Slack, you will need to fetch the Slack API from the server.

One way to solve this, is by exposing a backend API, for example:

Add service builder.Services.AddCors and app add app.UseCors("corsapp");

replace builder.WithOrigins("*") with builder.WithOrigins("http://localhost:800", "https://misite.com");

check documentation