What is Signal, the messaging app Donald Trump's team used to share war plans?

The app does not use US government encryption or that of any other governments, and is not hosted on government servers

(Left to right) Vice president JD Vance swears in Pete Hegseth to be secretary of defence as his wife Jennifer Rauchet holds the Bible and Hegseth's children watch in January. Top national security officials for US President Donald Trump, including his defence secretary, texted war plans for upcoming military strikes in Yemen to a group chat in a secure messaging app that included the editor-in-chief for The Atlantic. File photo: AP/Rod Lamkey, Jr

Top Trump administration officials used messaging app Signal to share war plans and mistakenly included a journalist in the encrypted chat, spurring calls by Democratic lawmakers for a congressional investigation into the security breach.

Under US law, it can be a crime to mishandle, misuse or abuse classified information, though it is unclear whether those provisions might have been violated in this case.