Parler has dropped offline after Amazon pulled support for its so-called "free speech" social network.
The platform had been reliant on the tech giant's Amazon Web Services (AWS) cloud computing service to provide its alternative to Twitter.
It is popular among supporters of Donald Trump, although the president is not a user.
Amazon took the action after finding dozens of posts on the service which it said encouraged violence.
Google and Apple had already removed Parler from their app stores towards the end of last week saying it had failed to comply with their content-moderation requirements.
However, it had still been accessible via the web - although visitors had complained of being unable to create new accounts over the weekend, without which it was not possible to view its content.
'All ditched us'
Parler has been online since 2018, and may return if it can find an alternative host.
However, chief executive John Matze told Fox News on Sunday that "every vendor from text message services to email providers to our lawyers all ditched us too".
"We're going to try our best to get back online as quickly as possible, but we're having a lot of trouble because every vendor we talk to says they won't work with us because if Apple doesn't approve and Google doesn't approve, they won't," he added.
AWS's move is the latest in a series of actions affecting social media following the rioting on Capitol Hill last week.
Facebook and Twitter have also banned President Trump's accounts on their platforms, citing concerns that he might incite further violence.
Parler's users included the Republican Senator Ted Cruz, who had led an effort in the Senate to delay certifying Joe Biden's electoral college victory.
He had about five million followers on the platform - more than his tally on Twitter.

"Why should a handful of Silicon Valley billionaires have a monopoly on political speech?" he tweeted over the weekend.
However, Amazon told Parler that it had seen a "steady increase in this violent content on your website, all of which violates our terms", adding that it did not believe the platform's administrators had an "effective process" that could tackle the problem.
Examples it provided include posts calling for the killing of Democrats, Muslims, Black Lives Matter leaders, and mainstream media journalists.
Parler's downfall appears to have benefited Gab - another "free speech" social network that is popular with far-right commentators.
It has claimed to have "gained more users in the past two days than we did in our first two years of existing".
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