The short answer: It is not recommended.
The long answer: French fries are potatoes that have been sliced into strips, deep fried, and usually served with heaps of salt and/or tomato sauce. Though your dog can eat ripe, cooked, and unflavoured potatoes, he should not be given French fries because of the canola or vegetable oil, salt, and other artificial condiments found in them. Canola or vegetable oil gives your fries unhealthy trans and saturated fats, while salt is known to be toxic for dogs.
Feeding your dog too many pieces of fries may make him vomit, make his stomach bloat, or make him experience the runs. Worse, he may end up suffering from acute gastroenteritis or pancreatitis. The salt can also cause him to become extremely thirsty and dehydrated.
What to do if your dog accidentally eats French fries: Observe your pet for any changes in his behaviour and peeing habits. Give him lots of drinking water, so he can quench his thirst. If your dog shows signs of severe allergic reaction (e.g. hives, swelling, and difficulty breathing), salt poisoning (e.g. confusion, seizure, vomiting, diarrhea, fever, drunk-like behaviour, and coma), or bloating (e.g. swollen stomach, drooling, panting, pacing, and abdominal pain), contact your veterinarian immediately.
In summary: Allowing your pooch to eat this greasy and salty snack may cause him to develop kidney problems and obesity in the long run. Keep the platter of French fries away from his line of sight and reach, so that he doesn’t become familiar with it and develop a taste for it. Instead of French fries, discover which human food dogs can safely eat in our “can dogs eat” category.