The Threads app launched by Instagram as a rival to Twitter has signed up more than 100 million users in less than five days, data tracking websites said on Monday, smashing the record of AI tool ChatGPT for fastest-growing consumer app.

While ChatGPT took two months to hit the 100 million user mark and video-sharing app TikTok took nine months, Instagram itself took two and a half years to reach that mark after its 2010 launch.

Threads went live on Apple and Android app stores in 100 countries late on Wednesday, though it is not available in Europe because parent company Meta is unsure how to navigate the European Unions data privacy legislation.

Twitter is thought to have around 200 million regular users but it has suffered repeated technical failures since Elon Musk bought the platform last year and sacked thousands of staff.

Musk, who also serves as the boss of Tesla and SpaceX, has also alienated many users by introducing charges for previously free services and allowing banned right-wing accounts back on the platform.

Several rivals have emerged but most are niche platforms without the capacity to grow at the necessary scale to dethrone Twitter.

Threads is finding it easier because it is linked to Instagram, which has more than one billion regular users.

Online data service Quiver Quantitative reported that the app passed 100 million users at 0700 GMT on Monday.

Other websites using a count of the badges received by Instagram users who have downloaded Threads reckoned the mark had passed earlier.

Musk has threatened to sue Meta for stealing trade secrets and intellectual property, claims denied by the company, which also owns Facebook and WhatsApp.

Musk is locked in a rivalry with Meta chief Mark Zuckerberg, with the two men calling each other out for a cage fight recently. (AFP)