I was personally unable to sync for ~ 20 minutes, but I can again now. There is more than one “AnkiWeb” server, and a whole world of internet, so it won’t stop and start for everyone at the exact same moment. Please be patient.
Me too! Was so stressed thinking it was an add-on I put on my Anki. It was messed up after that, not syncing. Anyway, I’m so glad it’s not just me and that they’re working on it!
No worries, thank you. I just have 2 years of work on it so I am a bit stressed
You’ve got all of your work on your own device. Anki is offline-first, so even if the AnkiWeb servers vanished from the earth (which I’m fairly sure isn’t what is happening today), you wouldn’t lose anything.
also down for me 
i can’t even go thru my cards
Ok awesome. Thank you so much
working now in Australia.
The issue should now be resolved. Thanks to everyone for their patience.
Sync is working now but I still can’t acess my decks on Ankiweb. It keeps returning 504.
Try clearing your cache and cookies for ankiweb.net and logging into the site again.