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Cross-Origin Read Blocking (CORB) when using webchat


I'm running my own implementation of a webchat using:

  • SAP Conversational AI webchat from
  • Chrome browser Version 75.0.3770.100 (Official Build) (64-bit) on Mac OS
  • Development website served locally (http://localhost:3000)

I get the following errors on the browser console:

1) only once, when first loading the webchat client.

xhr.js:160 GET 404

2) And the following, with each message sent by the user:

xhr.js:160 Cross-Origin Read Blocking (CORB) blocked cross-origin response with MIME type application/json.

The bot works well though. The only problem is that it doesn't recall what conversation it was in when the user refreshes the webpage on the browser.

Is it possible to whitelist "localhost"? Or any other setting that would prevent these errors?


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I had the exact same issue. In my case it turned out to be one or more of the below lines in the header of my index.html file. I had at some point added those lines in order to see whether I could prevent the chatbot from caching a conversation and open as a clean sheet at each page refresh. Those lines didn't do the trick but I never removed them. I then re-used the same html template for another bot and started having the same error as you namely, last_message_id 404. I removed those lines and the bot started working. Do you happen to have any such instructions in your index.html header? In addition try to see how the browser behaves in incognito mode. Does it give you the same error? Interestingly it didn't for me.

<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="Pragma" content="no-cache" />
<meta http-equiv="Expires" content="-1" />