Apple’s (aapl) App Store hit a major glitch Thursday morning that lasted for about six hours.
When users tried to search for apps, Apple returned with odd, unrelated, or simply incorrect results. The problem reportedly affected all users, and made it difficult to find even well-known apps such as YouTube, Google, and Vine.
It was a significant problem since nearly half of all iPhone users find or buy apps via the App Stores search function, according to 2014 data from analytics company TUNE.
“All users were affected,” Apple’s status update read. The problem seemed to begin around 5 a.m. ET and was later resolved around 11 a.m.
If a user tried to search for Spotify, the app store would pull up results related to music streaming—but not Spotify. Similarly, if a user attempted to search for Instagram, the engine brought back results in the “photography” category—but likewise, no Instagram.
Users on Twitter took notice:
In some cases, even links to external links to apps failed to work:
It’s still unclear what caused the glitch. Fortune has contacted Apple and will update this story if the company responds.