Brazilians had woken up shocked and cranky because of the order issued by a judge. The judge acted because the Facebook-owned service failed to disclose information requested by prosecutors as part of a criminal investigation.

The free service is widely used in Brazil where cell phone tariffs for texting and calls are among the highest in the world. The app is installed in nine in 10 smartphones in the country.

It was to have remain suspended until midnight Friday. But in the end, the cut-off lasted around 12 hours as a court in Sao Paulo overturned the judge's order.

"Because of constitutional principles, it is not reasonable that millions of users be affected," the Sao Paolo court overseen by judge Xavier de Souza wrote. Authorities said they could not disclose details of the probe that triggered the original ban because it is an ongoing case.

Many saw the complaint against WhatsApp as being driven by Brazil's telecoms companies trying to preserve their high-margin cell phone rates from competition from the free app.