1,386 independent third-party assays are published here, covering 879 compounds across 207 vendors.
An independent lab is one with no commercial relationship to the seller. That independence is the whole value of the result — a vendor's in-house number is a marketing claim regardless of how it is formatted, and vendor-supplied certificates are easy to fabricate and are fabricated.
What a certificate covers is one submitted lot on one date. It is not a rolling guarantee, and the vendor chose which lot to send, so a long testing history carries far more weight than one good result.
Reading one properly means checking four things: that the compound named matches what is sold, that a lot number is present, that the date is recent, and that identity was confirmed rather than only purity. Purity says how much of the sample is a single substance; it does not say which substance.
Results are published here exactly as the lab reported them, including where they contradict a vendor this site links to.
Related: Peptide Quality & Purity Testing, Peptide Vendor Directory, How We Rate Peptides and Vendors.