From 2019-09-06 17:50 UTC to 02:40 the next day, Wikimedia websites were affected by a denial-of-service attack.
The attack targeted different datacenters at different times. The Amsterdam datacenter was the most heavily affected, so users in Europe were the most likely to experience problems.
The attack saturated some network links, and thus caused some users to see timeouts or slow service across all hosted wikis.
Throughout the attack, the SRE team were working hard to restore service. Reports from individual affected users are not required -- monitoring systems recorded the effects of the attack at all times.
Blog post: https://wikimediafoundation.org/news/2019/09/07/malicious-attack-on-wikipedia-what-we-know-and-what-were-doing/