Facebook-owned Instagram was down for some users for around 45 minutes on Wednesday.
Users on Twitter complained about the service being down. CNBC also checked Instagram and the photo sharing app was unable to refresh the feed to show new pictures.
The hashtag "#instagramdown" began trending on Twitter just after 9 a.m. London time. Shortly after Instagram resumed normal service.
"We're aware that some users had trouble accessing Instagram. We have worked quickly and the issue is now resolved," an Instagram spokesperson told CNBC on Wednesday.