Although McDonald's will never claim gluten free on their menu because of cross contamination risk, they do have plenty of options that do not contain gluten.
With that being said check out their Nutrition Centre and download their ingredient guide. They list ingredients for all of their items, and indicate gluten when included in a menu item.
McDonald's french fries do not contain any gluten, and infact are fried in dedicated fryers due to the sheer volume of fries that are made.
A McDonald's hamburger patty does not contain any fillers, but always check the seasoning and sauces you put on it.
The new create your taste system allows you to customize your burger down to the T.
Did you know that you can order a lettuce wrap burger at McDonald's which gives you a quick and easy gluten free option with an order of fries?
Why is it important to check their website before each visit? The McDonald's ingredients list is often updated and quite extensive. Each section is split into two parts. It first lists off the menu item, and what comes with that menu item. It then lists ingredients of each element of that menu item. The document is 30 pages long, so it is quite extensive, as it should be.
What else do you need to know about eating at McDonald's? There is definitely a risk of cross contamination, so approach with caution. Just like when you are eating at any other restaurant ask if they can clean utensils and clean the food prep surface for you to help reduce the risk.