Short answer
You may eat there, but the meat and chicken are halal only if that branch serves certified zabiha meat, which most Western branches do not. Fries and other vegetarian items are halal only if they have no animal or alcohol ingredients and are not fried in oil shared with non-halal meat. AmalKit does not certify brands: check each branch and country.
Eating at a non-halal restaurant is permitted. Its meat and chicken are haram unless reliably known to be zabiha, and food cooked in the same oil or on the same surface as pork or non-zabiha meat becomes impure (najis) and must be avoided.
The four schools agree on this.
Explanation
The four schools agree on the principle: meat is halal only when it was slaughtered by the rules, and food that has touched impurity is not eaten. Fast food chains are no different from any other restaurant. The question is what this branch actually serves.
- Meat and chicken: in Muslim-majority countries, branches of big chains usually serve certified halal meat. In the US, UK and Canada most do not, though some individual branches do. Ask to see the certificate, and check what it says about hand slaughter.
- Fries and vegetarian items: check the company's ingredient list for your country. Flavourings can contain meat or dairy derivatives, and recipes differ between countries.
- Shared fryers and grills: if fries or fish are fried in the same oil as non-halal chicken, or a veggie patty is cooked on the bacon grill, the food is not halal.
- Fish: fish itself is halal, but check the batter and the fryer.
Staff saying yes it is halal is not the same as certification. Many workers do not know where the meat comes from. If you cannot find out, the safer choice is to leave it, as the Prophet ﷺ taught about doubtful things.
The same rules apply to sandwich chains, pizza places and chicken shops. Check single ingredients with the halal food checker, and see what makes meat halal.
The evidence
Quran, Surah Al-Baqara 2:168
يَٰٓأَيُّهَا ٱلنَّاسُ كُلُوا۟ مِمَّا فِى ٱلْأَرْضِ حَلَٰلًۭا طَيِّبًۭا وَلَا تَتَّبِعُوا۟ خُطُوَٰتِ ٱلشَّيْطَٰنِ ۚ إِنَّهُۥ لَكُمْ عَدُوٌّۭ مُّبِينٌ ﴿١٦٨﴾
O mankind, eat from whatever is on earth [that is] lawful and good and do not follow the footsteps of Satan. Indeed, he is to you a clear enemy.
Muslims eat what is both lawful and wholesome.
Sahih al-Bukhari 52
Sahih... الحلال بين والحرام بين وبينهما مشبهات ...
"The lawful is clear and the unlawful is clear, and between them are doubtful matters."
Shows how to treat food whose source you cannot confirm.
Jami' at-Tirmidhi 2518
Graded sahih... دع ما يريبك إلى ما لا يريبك ...
"Leave what makes you doubt for what does not make you doubt."
Supports leaving meat when the branch cannot confirm it is halal.
Where the ruling is recorded
- Radd al-Muhtar (Ibn Abidin), Kitab al-Taharah, chapter on impurities. Oil and food that touch an impure substance become impure.
- al-Fatawa al-Hindiyya, Kitab al-Karahiyya. Rules on food from non-Muslim sources and doubtful meat.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.