Users are instead greeted with empty profiles and a message that the app "cannot refresh feed".
The web version of the app also has problems. Heading to any page brings up only a "5xx Server Error".
Issues are particularly affecting users in northern Europe, Australia and the west coast of the US, according to the outage-tracking website Down Detector. But that is probably because of time zones – in California, where Instagram is based, it is past midnight.
The problems come amid a difficult time for Instagram. The company's two founders left in recent days amid rumours that it disagreed with Facebook over how the company should be run.
And after the Facebook hack was revealed over the weekend, it emerged that Instagram users and accounts might also have been caught up in it if they had used their Facebook log-in to create their Instagram account.
Some of the accounts caught up in Facebook's hacks appear to be trading on the dark web, with cyber criminals able to buy access to people's accounts for just a few dollars, according to listings seen by The Independent.
It's not thought that those issues have anything to do with the current outage, which is almost certainly simply a technical fault. Instagram goes down for time-to-time and can send major ripples across the internet, since more than a billion people use it each month.
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