There is no difference in meaning: "Everybody knows the rules" and "Everyone knows the rules" say the same thing. Everyone is slightly more formal and turns up more often in edited writing; everybody sounds a shade more conversational. Both take a singular verb.
This is one of the rare pairs where the honest answer is that the two words are interchangeable. Any writing guide claiming a rule about which one to use in which situation is describing a preference, not grammar.
What real difference exists is one of register. Everyone is somewhat more formal and appears more often in books, journalism and business writing. Everybody is a little warmer and more spoken. Choose by ear: "Everyone is asked to remain seated" for an announcement; "Everybody grab a chair" in a room full of friends.
The grammar both share
Both are singular. They take a singular verb even though they refer to a group:
- "Everyone is here." (not are)
- "Everybody has signed the form." (not have)
Both take their as a follow-on pronoun in ordinary modern usage: "Everyone brought their own lunch." This has been standard in English for centuries and is accepted by every major style guide today. The old advice to write "his or her" produces clumsy sentences and is now largely abandoned.
The test that actually matters
The genuine trap in this area is not everybody against everyone — it is everyone against every one (two words). Try inserting of after the word. If of fits, use two words:
- "Every one of the windows was broken." (of fits — two words)
- "Everyone was late." ("everyone of was late" is nonsense — one word)
Every one picks out members of a specified set individually, and it can refer to things: "I checked the boxes and every one was empty." Everyone refers only to people.
The same split applies to everybody, which never separates — there is no "every body" in this sense, except in the literal medical or forensic one.
Which to choose
If you are writing a formal report, a legal notice or an academic paper, everyone is the safer default. In email, dialogue, marketing copy or speech, either is fine and everybody often reads more naturally. What matters far more is consistency within a piece: pick one for a given document and stay with it.
Frequently Asked Questions
Is everyone more correct than everybody?
No. Both are fully correct. Everyone is slightly more formal and commoner in print, but neither is a mistake in any context.
Is it "everyone is" or "everyone are"?
"Everyone is." Both everyone and everybody are grammatically singular, even though they refer to lots of people.
When do I write "every one" as two words?
When you mean each individual member of a known group, and especially when of follows: "Every one of the tickets sold." One word (everyone) always means all the people.