WhatsApp will stop working on older smartphones from 1 January 2018 as the company pulls support for older operating systems.
Explaining the move to pull support, WhatsApp said that when it was founded in 2009 the mobile landscape was very different.
"About 70% of smartphones sold at the time had operating systems offered by BlackBerry and Nokia," the company explained.
"Mobile operating systems offered by Google, Apple and Microsoft – which account for 99.5% of sales today – were on less than 25% of mobile devices sold at the time."
The full list of unsupported mobile operating systems is:
:: BlackBerry OS and BlackBerry 10
:: Nokia S40
:: Nokia Symbian S60
:: Android 2.1 and Android 2.2
:: Windows Phone 7
:: iPhone 3GS/iOS 6
For most WhatsApp users, pulling support for older operating system (OS) versions will not really be noticeable.
The most recent Android OS that WhatsApp will no longer be supported on, 2.2 or "Froyo", was released more than seven years ago on 20 May 2010.
Statistics released last January by Google, which develops Android, indicated that less than 0.1% of all Android devices still ran Froyo.
The most recent Android release 8.0 or "Oreo" was released on 21 August 2017.
For Apple users, iOS 6 was released on 19 September 2012, and was succeeded by iOS 7 in 2013. Less than 0.03% of iPhone users are currently using iOS 6.
The most recent version of Apple's mobile operating system is iOS 11 was released on 19 September 2017.
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Blackberry OS has less than 0.5% of the smartphone operating system market share in the UK.
Windows Phone is only run by roughly 1% of UK smartphone users, many of whom will be on later versions of the Windows Phone OS.