Hi @petercj. @van_der_decken already provided a link to the solution I recommend, but in case more detailed instructions might be useful, I'll provide them here:
- Select File > Preferences... (or Arduino IDE > Settings... for macOS users) from the Arduino IDE menus.
The "Preferences" dialog will open. - Replace the nonfunctional URL (
http://drazzy.com/package_drazzy.com_index.json) in the "Additional Boards Manager URLs" field with this URL:https://raw.githubusercontent.com/SpenceKonde/ReleaseScripts/refs/heads/master/package_drazzy.com_index.json - Click the "OK" button.
The "Preferences" dialog will close. - You will now see a "Downloading index: ..." notification at the bottom right corner of the IDE window. Wait for that notification to close.
The index download should complete successfully and you should now be able to install ATTinyCore as usual.
The URL I provided is the original source file of the one at http://drazzy.com/package_drazzy.com_index.json, hosted in a repository under SpenceKonde/DrAzzy's own GitHub account. So this new URL is trustworthy and should be functional even long term. However, I do think it is generally best practices to use the URL specified by the platform author. So you might want to monitor the reports about the issue and then change the URL back to the canonical http://drazzy.com/package_drazzy.com_index.json once Spence reports the certificate has been renewed. I see it was mentioned here (the issue was created in response to a previous occurrence, but Spence never closed it and so it has been reused to report additional occurrences as well):
and a dedicated issue for the current occurrence here:
and here:
(the same package index URL is used for all of Spence's platforms, so the issue in the DxCore platform's tracker also applies to the problem affecting ATTinyCore users)
If you have a GitHub account, you can subscribe to that thread to get notifications of any new developments on that issue report:
