Microsoft's Windows Store now boasts a library of 20,000 apps, according to a Twitter post by tracker site Win App Update. The number reflects a global estimate, as few apps are available in all regions.

The online marketplace has a grand tally of 20,610 apps worldwide, with 87 per cent, or 17,958, of those being free to download.

Most apps are region-specific, due to factors pertaining to licensing, language and cultural relevance. The UK currently has access to approximately 11,000 apps, with Canada enjoying the lion's share of the store's bounty with 14,000 apps available there. Microsoft's domestic market, the US, enjoys the second-largest portion, with 13,000 apps.

Additional reports estimate that 7,715 apps were added to the store over a period of 17 days - that's around 453 apps per day. If app development continues at this pace, the Windows Store will likely pass the 30,000 apps milestone by the end of the year.

Microsoft still has a ways to go before it can match the 700,000 app libraries that its competitors Apple and Google currently boast. However, the rate of growth is an encouraging sign for Windows 8 owners that the new platform will continue to attract third party support.