Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally, until cooked through but firm to the bite, 8 minutes; drain.
Rinse macaroni in cold water until cool; drain.
Stir mayonnaise, onion, parsley, mustard, rice vinegar, sugar, celery seed, and salt together in a bowl; add macaroni and eggs and stir to coat.
Chill in refrigerate for 30 minutes before serving.
