Both "everyday" and "every day" are correct, but they have different meanings and usage.
"Everyday" is an adjective that means ordinary, commonplace, or routine. For example: "I wear everyday clothes to work."
"Every day" is an adverb phrase that means each day or daily. For example: "I go to the gym every day."
So, if you are using "everyday" as an adjective to describe a noun, you don't need to separate the two words. However, if you want to convey the meaning of "each day" or "daily," then you should use "every day" as two separate words.
Here are some examples to help illustrate the difference:
She wears everyday clothes to work. (adjective)
She walks her dog every day. (adverb phrase)
He enjoys his everyday routine. (adjective)
He practices the piano every day. (adverb phrase)