This morning, Telegram users on WhatsApp noticed something strange. The chat app was blocking any links to Telegram.me, a rival chat app that grew popular in the wake of earlier WhatsApp outages. The URLs still appeared as messages, but they did not register as hyperlinks and users were blocked from copying them to paste into another app — effectively treating them like malware or spam. The behavior wasn't exhibited on every device but it was consistent within devices, blocking both usernames and links to individual messages or chat rooms.

Reached by The Verge, Telegram confirmed the activity, which seems to have begun with a silent update pushed earlier this morning. The update has the same version number as a previously deployed update (2.12.367), but a Telegram volunteer confirmed that a new 367 update was deployed this morning. That update likely hasn't reached every device using WhatsApp, which may explain why the block is not consistent across different devices. Testing revealed that the block also includes Telegram.com, an unrelated URL owned by a newspaper in Worcester, Massachusetts.

An example shared on /r/Telegram

Those link-blocks are a common tool at Facebook, which owns WhatsApp, although they've been controversial in the past. In 2010, Facebook faced criticism for blocking Pirate Bay links in the newly unveiled messaging system, after a long history of blocking similar apps on the News Feed. More recently, it drew criticism for blocking any mention of the social network Tsu.co, which pays users a percentage of its ad revenue for each post. But while those blocks are a regular occurrence within Facebook proper, this is the first major link-block we've seen from WhatsApp.

It remains to be seen whether the link is a purposeful move against Telegram or an unintentional glitch, but Telegram doesn't seem worried. "Typically after a media backlash, FB steps back and blames their intelligent filtering for the problem," a Telegram spokesperson said. "We expect the same to happen this time as well." Facebook and WhatsApp did not respond to a request for comment; we will update with any response.