Third-party testing means an independent laboratory verifies that a supplement contains what its label says and does not contain harmful contaminants. It is the strongest quality assurance available.
Ingredient identity (is it actually turmeric?). Potency (does it contain the labeled amount?). Purity (free of heavy metals, pesticides, microbial contamination). Dissolution (will the capsule dissolve and release its contents?).
USP (United States Pharmacopeia), NSF International, ConsumerLab, and Informed Choice are the most recognized third-party testing organizations.
Third-party testing is voluntary. Many products, including most supplement-brand-direct products, do not carry independent certifications. GMP certification addresses manufacturing quality but does not substitute for product-level independent testing.