Who makes Kirkland Signature Professional Salon Formula Moisture Shampoo & Conditioner (33.8 fl oz)?

What most answers say — and what the evidence supports

The best-known claim is that Kirkland Signature Moisture Shampoo comes from the same manufacturer as Pureology (a L'Oreal-owned brand) - essentially a Pureology dupe; a newer theory points to Olaplex instead, based on ingredient overlap. Neither claim is backed by hard evidence; both rest on formula and scent similarity, and Costco reformulated the product in 2021 and again in 2023, after which reviewers stopped calling it a Pureology match. Costco's product-detail data names Cosway Company, Inc. as the manufacturer of record for both the shampoo and the conditioner, so the evidence points to Cosway rather than Pureology or Olaplex.