This post is a wiki post. Anybody can edit it to provide useful tips for whitelisting. Editing abuse may result in a ban from the forums!
Whitelisting Tips
List any tips you've discovered on how or what to whitelist in order to solve specific issues!
Google (Maps, Youtube, etc)
Google Maps and other Google services
pihole -w clients4.google.com
pihole -w clients2.google.com
YouTube history
pihole -w s.youtube.com
pihole -w video-stats.l.google.com
Google Play
As described here.
pihole -w android.clients.google.com
Google Keep
The Google Keep Chrome App requires these domains to be whitelisted in order to sync.pihole -w reminders-pa.googleapis.com firestore.googleapis.com
Gmail (Google Mail)
iOS app requires this to be whitelisted for the app to connect.pihole -w googleapis.l.google.com
Microsoft (Windows, Office, Skype, etc)
Windows uses this to verify connectivity to Internet
pihole -w www.msftncsi.com
Microsoft Web Pages (Outlook, Office365, Live, Microsoft.com...)
pihole -w outlook.office365.com products.office.com c.s-microsoft.com i.s-microsoft.com login.live.com login.microsoftonline.com
Backup bitlocker recovery key to Microsoft account
pihole -w g.live.com
Microsoft Store (Windows Store)
pihole -w dl.delivery.mp.microsoft.com geo-prod.do.dsp.mp.microsoft.com displaycatalog.mp.microsoft.com
Xbox Live
This domain is used for sign-ins, creating new accounts, and recovering existing Microsoft accounts on your (confirmed by Microsoft)
pihole -w clientconfig.passport.net
These domains are used for Xbox Live Achievements (confirmed by Microsoft)
pihole -w v10.events.data.microsoft.com
pihole -w v20.events.data.microsoft.com
Used for Xbox Live Messaging (post)
pihole -w client-s.gateway.messenger.live.com
There are several domains discovered initially on Reddit and /r/xboxone, which were also confirmed by Microsoft as being required by Xbox Live for full functionality.
pihole -w xbox.ipv6.microsoft.com device.auth.xboxlive.com www.msftncsi.com title.mgt.xboxlive.com xsts.auth.xboxlive.com title.auth.xboxlive.com ctldl.windowsupdate.com attestation.xboxlive.com xboxexperiencesprod.experimentation.xboxlive.com xflight.xboxlive.com cert.mgt.xboxlive.com xkms.xboxlive.com def-vef.xboxlive.com notify.xboxlive.com help.ui.xboxlive.com licensing.xboxlive.com eds.xboxlive.com www.xboxlive.com v10.vortex-win.data.microsoft.com settings-win.data.microsoft.com
Skype
See the GitHub Topic on these domains.
pihole -w s.gateway.messenger.live.com client-s.gateway.messenger.live.com ui.skype.com pricelist.skype.com apps.skype.com m.hotmail.com sa.symcb.com s{1..5}.symcb.com
Microsoft Office
Reddit link - r/pihole - MS Office issues
pihole -w officeclient.microsoft.com
Jackbox.tv
Jackbox.tv will not load unless you whitelist google-analytics
pihole -w www.google-analytics.com
pihole -w ssl.google-analytics.com
Spotify
The Spotify app for iOS will stop functioning unless it's web service counterpart is whitelisted.
pihole -w spclient.wg.spotify.com apresolve.spotify.com
Target's Weekly Ads
pihole -w weeklyad.target.com m.weeklyad.target.com weeklyad.target.com.edgesuite.net
Facebook, Facebook Messenger
pihole -w upload.facebook.com creative.ak.fbcdn.net external-lhr0-1.xx.fbcdn.net external-lhr1-1.xx.fbcdn.net external-lhr10-1.xx.fbcdn.net external-lhr2-1.xx.fbcdn.net external-lhr3-1.xx.fbcdn.net external-lhr4-1.xx.fbcdn.net external-lhr5-1.xx.fbcdn.net external-lhr6-1.xx.fbcdn.net external-lhr7-1.xx.fbcdn.net external-lhr8-1.xx.fbcdn.net external-lhr9-1.xx.fbcdn.net fbcdn-creative-a.akamaihd.net scontent-lhr3-1.xx.fbcdn.net scontent.xx.fbcdn.net scontent.fgdl5-1.fna.fbcdn.net graph.facebook.com b-graph.facebook.com connect.facebook.com cdn.fbsbx.com api.facebook.com edge-mqtt.facebook.com mqtt.c10r.facebook.com portal.fb.com star.c10r.facebook.com star-mini.c10r.facebook.com b-api.facebook.com fb.me bigzipfiles.facebook.com l.facebook.com
DirectTV
Sourced from here.
pihole -w directvnow.com directvapplications.hb.omtrdc.net s.zkcdn.net js.maxmind.com
Bild DE
pihole -w ec-ns.sascdn.com
Plex Domains
pihole -w plex.tv tvdb2.plex.tv pubsub.plex.bz proxy.plex.bz proxy02.pop.ord.plex.bz cpms.spop10.ams.plex.bz meta-db-worker02.pop.ric.plex.bz meta.plex.bz tvthemes.plexapp.com.cdn.cloudflare.net tvthemes.plexapp.com 106c06cd218b007d-b1e8a1331f68446599e96a4b46a050f5.ams.plex.services meta.plex.tv cpms35.spop10.ams.plex.bz proxy.plex.tv metrics.plex.tv pubsub.plex.tv status.plex.tv www.plex.tv node.plexapp.com nine.plugins.plexapp.com staging.plex.tv app.plex.tv o1.email.plex.tv o2.sg0.plex.tv dashboard.plex.tv
Domains used by Plex
pihole -w gravatar.com - custom login pictures
pihole -w thetvdb.com - metadata for tv series
pihole -w themoviedb.com - metadata for movies
Sonarr
pihole -w services.sonarr.tv skyhook.sonarr.tv download.sonarr.tv apt.sonarr.tv forums.sonarr.tv
Placehold.it (Image placeholders often used during web design. Not sure why this is even blocked in the first place.)
pihole -w placehold.it placeholdit.imgix.net
Dropbox
As described here:
pihole -w dl.dropboxusercontent.com ns1.dropbox.com ns2.dropbox.com
Fox News
as described here.
pihole -w widget-cdn.rpxnow.com
Images on Marketwatch.com
pihole -w s.marketwatch.com
Apple Music
pihole -w itunes.apple.com
pihole -w s.mzstatic.com
GoDaddy webmail buttons
pihole -w imagesak.secureserver.net
Google Chrome (to update on ubuntu)
pihole -w dl.google.com
Apple ID
pihole -w appleid.apple.com
WatchESPN
as described here.
pihole -w fpdownload.adobe.com entitlement.auth.adobe.com livepassdl.conviva.com
NVIDIA GeForce Experience
GFE requires this to download driver updates (or events.gfe.nvidia.com, but that is also used for telemetry).
pihole -w gfwsl.geforce.com
Videos not playing in times.com and nydailynews.com
pihole -w delivery.vidible.tv img.vidible.tv videos.vidible.tv edge.api.brightcove.com cdn.vidible.tv
Bing Maps Platform
as described here.
pihole -w dev.virtualearth.net ecn.dev.virtualearth.net t0.ssl.ak.dynamic.tiles.virtualearth.net t0.ssl.ak.tiles.virtualearth.net
Google Play Android updates
pihole -w android.clients.google.com
Moto phones OS updates
pihole -w appspot-preview.l.google.com
Captive-portal tests
These domains are checked by the operating systems when connecting via wifi, and if they don't get the response they expect, they may try to open a wifi login page or similar as they believe they are located behind a captive portal.
Android/Chrome
pihole -w connectivitycheck.android.com android.clients.google.com clients3.google.com connectivitycheck.gstatic.com
Windows/Microsoft
pihole -w msftncsi.com www.msftncsi.com ipv6.msftncsi.com
iOS/Apple
(note that this does not cover all domains used older iOS versions)
pihole -w captive.apple.com gsp1.apple.com www.apple.com www.appleiphonecell.com
Grand Theft Auto V Online PC
Since March blocking Rockstar telemetry seems to crash GTAOnline.
Unblocking the domain fixed crashing for people at GTA Forums.
pihole -w prod.telemetry.ros.rockstargames.com
Chevrolet
Couldn't browse inventory w/o whitelisting
pihole -w chevrolet.com
Epic Games Store
The tracking domain is required to make a purchase on the website, otherwise the order modal will appear to be loading forever.
It is also required when logging into the Epic Launcher when using two-factor authentication.
pihole -w tracking.epicgames.com
Red Hat Online Learning (subscription required)
embedded video player
When blocked, video would play; however, not show progress (continually showing it was loading) and thus not record your progression through the video in the course progress tracker.
pihole -w 79423.analytics.edgekey.net
Lowe's Checkout
Clicking "Start Secure Checkout" from the Shopping Cart on Lowe's website does not load anything.
pihole -w assets.adobedtm.com
Home Depot Checkout
Clicking "Checkout" from the Shopping Cart on Home Depot's website takes you to a page to check out as guest, login, or create account. Entering login credentials does not ungray the "Sign In" option. "Checkout as a Guest" and "Create an Account" options do not load anything.
pihole -w nexus.ensighten.com