Is it permissible to eat meat from restaurants if it is not known whether Allah's name was mentioned over it at the time of slaughtering or not?

It is permissible to eat from restaurants in countries where Muslims or People of the Book slaughter animals, even if it is not known whether the name of Allah was mentioned over the slaughtered animal or not. This is because the default ruling is that their slaughtered animals are lawful. This is also supported by the Hadith (definition) of Aisha (may Allah be pleased with her) where a group of people said: "O Messenger of Allah, some people bring us meat, and we do not know whether they mentioned the name of Allah over it or not?" He replied: "Mention the name of Allah over it yourselves and eat it."

However, if the slaughtering is performed by non-Muslims or non-People of the Book, such as atheists or Hindus, then it is not permissible to eat from it.

Furthermore, a slaughtered animal is permissible if it was slaughtered according to Islamic law, or if the method of slaughtering is unknown. However, if it is known that it was slaughtered in an un-Islamic manner, such as by strangulation or electrocution, then it is considered carrion (maytah (definition)) and it is forbidden to eat from it, based on the words of Allah Almighty: "Forbidden to you are carrion, and blood, and the flesh of swine, and that which has been dedicated to other than Allah, and the strangled animal, and that beaten to death, and that which falls from a height, and that which is gored to death, and that which has been partly eaten by a wild animal – except that which you slaughter [in the proper way]."

So, if it is known that it was slaughtered in a sound manner, it is permissible. If it is known that it was slaughtered in an unsound manner, it is forbidden.

If there is doubt about the method of slaughtering, the slaughtered animal is permissible. There is no need to ask or investigate; in fact, it is better not to ask. This is in accordance with the Prophet's (peace be upon him) command to mention Allah's name before eating, which is a mention for the act of eating, not for the slaughtering which has already taken place.

If one refrains from eating out of scrupulousness, there is no blame upon him. And if one eats it, there is no blame upon him either.