The Telegram messaging apps appear to have breached Apple’s App Store guidelines and are currently unavailable for download on iOS. 9to5Mac spotted the absence yesterday, having been alerted via a Reddit thread.

At the time of writing a search for Telegram on the App Store returns Viber, Skype, Messenger and WeChat chat apps, as the top results, but not Telegram.

Both the original Telegram app and a rebuild, called Telegram X, which the messaging company officially announced for Android yesterday — billing it as a coding experiment aimed at speeding up development of the platform — have been taken off the iOS App Store for now.

It’s not entirely clear what the problem is. But responding to a Twitter user’s question, about why both its iOS apps are AWOL, Telegram founder Pavel Durov tweeted that it relates to “inappropriate content”.

“We were alerted by Apple that inappropriate content was made available to our users and both apps were taken off the App Store. Once we have protections in place we expect the apps to be back on the App Store,” he wrote.

We’ve reached out to Apple and Telegram with questions and will update this story with any additional information.

Apple’s developer guidelines for iOS apps include a section on safety that proscribes “upsetting or offensive content”. A sub-section here, regarding user-generated content (which would apply to any messaging app with a public broadcast facility, as Telegram has), notes these types of apps “present particular challenges” — and must therefore contain:

A method for filtering objectionable material from being posted to the app
A mechanism to report offensive content and timely responses to concerns
The ability to block abusive users from the service
Published contact information so users can easily reach you

“Apps with user-generated content or services that end up being used primarily for pornographic content, objectification of real people (e.g. “hot-or-not” voting), making physical threats, or bullying do not belong on the App Store and may be removed without notice,” the iOS guidelines add.

Why rebuild it?

In its blog officially announcing Telegram X for Android yesterday, the company describes the rebuilt and redesigned app as “experimental”, saying it “may or may not eventually replace the existing official app”.

“But even if it doesn’t, it will speed up the development of Telegram by allowing us to quickly test new approaches and technologies,” it added.

As well as being billed as faster and more battery efficient, Telegram X features a refreshed UX, with a cleaner look, smoother animations and new swiping actions for shortcutting.

An iOS version of Telegram X apparently appeared on Product Hunt in December. Before vanishing from the App Store at the end of last month — on “inappropriate content” grounds.

The Telegram X blog post doesn’t make mention of payments. But, as we reported last month, the company is gearing up to join the cryptocurrency craze — by launching its own ICO, with a plan to raise $1.2BN to finance a transformation from messaging platform into fully fledged blockchain network for hosting decentralized apps, a la Ethereum.

Given that sizable ambition, twinning Telegram and beginning again from scratch — with “an entirely new code base and without all the legacy components that our older apps have accumulated through the years,” as Telegram tells it — could also be Durov’s way of quietly laying the groundwork for retooling his platform as a blockchain.

According to the technical launch schedule in the white paper we’ve reviewed, Q2 is the slated timeframe for conducting an MVP test of the Telegram Open Network.

Thus far Durov has remained tight-lipped on the plans — though he has broken his silence to warn people away from scam offers to “buy Grams” (the purported name of the incoming Telegram token). But perhaps Telegram X marks the spot.