Application programming interface, or API, is a set of protocols for building and integrating application software.
Downdetector, which tracks outages by collating status reports from a number of sources, including user-submitted errors on its platform, showed over 48,000 user reports of outage.
The micro-blogging site said on its status page https://api.twitterstat.us it is yet to determine the scope of impact on its users.
Some users on Reddit complained of being logged out of their Twitter account while others said they could not send or retrieve tweets.
Twitter did not immediately respond to a request for comment.
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