What's the difference between third-party and in-house testing?

In-house testing means the company that makes or sells the peptide runs the analysis on its own equipment. Third-party testing means an outside, independent lab with no stake in the sale does it. The difference is the conflict of interest. When the seller grades its own work, there's a built-in pull to report favorable purity or potency. An independent lab removes that. Many independent labs also hold ISO/IEC 17025 accreditation, which an in-house bench may not. Labs like Janoshik publish results to a portal you can search by batch ID without going through the vendor. One caveat: a third-party COA usually reflects only the sample the vendor chose to send, which isn't always what ships. Finnrick says it anonymizes samples for this reason. So independent is better than in-house, but it isn't proof your vial matches. These are research-use-only materials, not approved for human use.