Everyday and every day are pronounced the same but are not interchangeable.
Everyday is an adjective that means ordinary, routine, or commonplace.
Example: I will now eat fruits and vegetables everyday.
Every day is an adverb that means each day.
Example: Every day is a new opportunity to correct whatever mistake was done the previous day.
Tip: To check whether you’re using the correct word, try using “each day”. If each day works on the sentence, then every day can be used. If it sounds wrong, then everyday should be used.