Invalid response received

I have a spring boot backend webapplication. I use org.web3j core libary(4.5.5).
I create a web3j interface:

String ethereumBaseUrl = “”;

Web3j web3j = HttpService(ethereumBaseUrl + Constant.ETH_PUBLIC_KEY));

After that I check the connection the:


And I received the ClientConnectionException with a following message:
Invalid response received: 403; {“jsonrpc”:“2.0”,“id”:0,“error”:{“code”:-32600,“message”:“project ID is required”,“data”:{“reason”:“project ID not provided”,“see”:“”}}}

This code was working a few weeks ago.
What is wrong?
Thx for your help.

Hi @gergenye, you will need to use our latest v3 authentication format, you can signup at and get started on our free Core tier and get your updated URL.

Let me know if you have any questions!