Correct spelling, explanation: swapped is a past simple form/past participle form/adjective participle of the infinitive to swap. As you can see, its construction is based on two elements: the root and the suffix. However, the last consonant must be doubled – because of an important rule: when there is a single vowel before the last (and stressed as well) consonant in a word, we have to double that consonant. That’s the reason the only correct version is swapped and swaped is just a mistake.

Definition of swapped:
1. verb (past simple, past participle), to replace one thing with another
When I was in the theatre with my daughter, we swapped places so she could’ve seen better.
My parents have swapped roles for one day. It was really funny.
2. adjective participle, to make an exchange
My shift in work was swapped with my colleague’s shift.
Alex’s bike was swapped for money.

Proverbs with swapped:
Some most commonly used proverbs include: Don’t swap horses at midstream, meaning: choose a sensible moment to change your mind.

Incorrect spelling, explanation: swaped is a spelling mistake because it doesn’t consist of the double -p letter, which is necessary in this case. Swap is a regular verb, which means that its conjugation shouldn’t be a problem for anyone. You need to add the suffix -ed to the end of the root. Although, we have to remember one principle: when there is a single vowel before the last and stressed consonant in a word, this consonant must be doubled. That’s why swapped is correct and swaped is not.