Localhost uses unsupported protocol

Question

I am trying to run an Asp.net Core application using Visual Studio 2019 in Chrome browser but i'm getting the following error:

"This site can’t provide a secure connection localhost uses an unsupported protocol. ERR_SSL_VERSION_OR_CIPHER_MISMATCH Unsupported protocol The client and server don't support a common SSL protocol version or cipher suite."

I tried repairing IIS Express 10, clearing browser data and certificates cache, deleting .vs folder,

But My .NET Core web apps are not working in Chrome. How to solve this??

I am not familiar with IIES express 10 but check to see which TLS protocol is enabled .. Make sure to enable TLS v1.2 and higher — Yan, Mar 02 '22 at 19:26
Check this SO question https://stackoverflow.com/questions/33761919/tls-1-2-in-net-framework-4-0 it might help — Yan, Mar 02 '22 at 19:32
I think you may try to [delete the self-signed certification](https://www.ryadel.com/en/visual-studio-localhost-self-signed-ssl-certificate-expired-warning-browser-fix/) and add a new one when running your application again. And I also agree with Yan's idea to check the [TLS version](https://learn.microsoft.com/en-us/mem/configmgr/core/plan-design/security/enable-tls-1-2) — Tiny Wang, Mar 03 '22 at 02:13

score 1 · Answer 1 · edited Aug 04 '22 at 02:15

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Try putting this URL in your Chrome browser to turn this flag on and then relaunch Chrome:

chrome://flags/#allow-insecure-localhost

edited Aug 04 '22 at 02:15

Jeremy Caney

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answered Aug 02 '22 at 10:12

kamal soni

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It seems like he is having issues with the set TLS version, making it insecure would not help around that. – Stephan Aug 06 '22 at 17:49
Seems he is using it in his local for development so thats why I said that. – kamal soni Oct 12 '22 at 12:45

Localhost uses unsupported protocol

1 Answers1