Error downloading https://downloads.arduino.cc/libraries/library_index.json

I keep getting this error, any thoughts how to fix it?

 Error downloading https://downloads.arduino.cc/libraries/library_index.json
java.lang.RuntimeException: java.lang.Exception: Error downloading https://downloads.arduino.cc/libraries/library_index.json
	at cc.arduino.contributions.libraries.ui.LibraryManagerUI.lambda$onUpdatePressed$2(LibraryManagerUI.java:207)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.Exception: Error downloading https://downloads.arduino.cc/libraries/library_index.json
	at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:144)
	at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:125)
	at cc.arduino.contributions.JsonDownloader.download(JsonDownloader.java:49)
	at cc.arduino.contributions.GZippedJsonDownloader.download(GZippedJsonDownloader.java:66)
	at cc.arduino.contributions.libraries.LibraryInstaller.updateIndex(LibraryInstaller.java:84)
	at cc.arduino.contributions.libraries.ui.LibraryManagerUI.lambda$onUpdatePressed$2(LibraryManagerUI.java:203)
	... 1 more
Caused by: java.net.UnknownHostException: downloads.arduino.cc
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:589)
	at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:666)
	at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
	at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
	at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
	at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:264)
	at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:367)
	at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1199)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050)
	at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
	at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162)
	at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150)
	at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:106)
	at cc.arduino.utils.network.FileDownloaderCache.updateCacheInfo(FileDownloaderCache.java:184)
	at cc.arduino.utils.network.FileDownloaderCache.getFileCached(FileDownloaderCache.java:153)
	at cc.arduino.utils.network.FileDownloader.downloadFile(FileDownloader.java:167)
	at cc.arduino.utils.network.FileDownloader.download(FileDownloader.java:129)
	at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:142)
	... 6 more

Stick https://downloads.arduino.cc/libraries/library_index.json into the URL bar of your browser and see if it loads up without an unknown host error.

If it doesn't, then it's probably some sort of external network problem; maybe just wait a day and see if it fixes itself. If it does, and you are still getting the error, then you should tell us what operating system you are using and what version of the IDE. If you are not using the latest IDE, then consider removing the older version and installing the newer.

it seems to work fine in the browser, I completely uninstalled it and reinstalled the latest and greatest version, and am still getting the error. I just noticed this morning that it gives the error as soon as I start arduino. not just when I go to add a new library.

windows 10 by the way... forgot to mention

anda arduino version 1.8.10

It may be a Java related problem, not Arduino : try troubleshooting the Java installation