This error typically appears with the following message:

"400. That's an error. The server cannot process the request because it is malformed. It should not be retried. That's all we know."

Below are the steps to identify and resolve the issue.

Common Extensions Causing the Issue

The following extensions have been reported to trigger the Google Calendar 400 error:

DuckDuckGo
Bitdefender Anti-tracker

These extensions override the URL that directs the event details to Google Calendar, resulting in a malformed request.

How to Resolve the Issue

To resolve this issue, you can disable the problematic browser extension by following these steps:

Access the Extensions Page: Open your browser and type in chrome://extensions/ in the URL or address bar.
Find the Extension: Look through the list of installed extensions to locate the problematic one (e.g., DuckDuckGo or Bitdefender Anti-Tracker).
Deactivate the Extension: Use the toggle switch (on/off button) in the bottom-right corner of the extension card to turn it off.
Retry Adding the Event: After disabling the extension, try adding the event to Google Calendar again.

What are the extensions doing wrong?

When you or your users click an Add to Calendar button and select Google Calendar, AddEvent redirects the user to Google Calendar with a specific URL format. This URL includes all the necessary event details. Here's an example of what that URL might look like:

https://calendar.google.com/calendar/render?action=TEMPLATE&text=Summary+of+the+event.....&sf=true&output=xml

Extensions like DuckDuckGo or Bitdefender intercept and alter this URL before it reaches Google Calendar. Instead of passing the correct information, they redirect the URL to an unintended location within Google's system. This manipulation causes Google Calendar to respond with the 400 error because it cannot process the altered request.

Additional Notes

If disabling the extension resolves the issue, you may re-enable the extension after adding the event or explore whitelisting options within the extension settings.
If the issue persists or additional help is needed, please contact our support team for assistance.