Methodology: how listings are checked

Prepared by: Research Desk. Sources are linked for verification.

This page explains how the quality signals in each directory listing are checked. Listings report documentation only. They never describe uses or effects of any product, and they are not rankings.

What is checked

Each listing is checked against eight documentation signals:

A testing laboratory named on published certificates of analysis (COAs).
A COA for each batch.
HPLC and mass spectrometry (MS) results on the COAs.
Batch or lot numbers matched to COAs.
Cold-chain shipping.
Documentation: safety data sheets, a named business entity and a business address.
Research-use labelling.
A written return and replacement policy.

How a check is done

Sources. Only the supplier's own public website is used: product pages, the certificates page, the terms, and the shipping and returns policy. Pages are read both as raw HTML and as rendered in a headless browser, because some store pages only show their content after scripts run.
COA files. Published COA files are downloaded and read. The laboratory name, method, purity figure, MS result, batch number and analysis date are noted as printed.
Dates. Every check has a date. A signal is shown as "Verified" with the date it was seen.

What "Verified" means

"Verified" means the signal was seen on the supplier's website, or in a document published there, on the date shown. It does not mean the information was confirmed with the testing laboratory, and it is not a statement about product quality.

Signals that could not be confirmed are left out of the listing rather than shown as unverified. Statements made by a supplier are reported as the supplier's own statements.

Example: Purita, checked 19 Oct 2026

Confirmed and shown: a testing laboratory named on the published COA files; HPLC and MS results on those files; a cold-chain shipping statement in the shipping policy; the operating company named in the terms; research-use labelling on all pages; a written return and replacement policy.
Not confirmed and left out: a COA for each batch, because the certificates page showed COA files for 5 of 21 listed products and "Coming soon" for the rest; batch numbers matched to containers, because no listing showed which lot ships; safety data sheets and a street address, which were not found.
Notes recorded: two COA files read for different compounds showed the same batch number, and the COA files name a client company other than the store.

What payment does not change

Some links on this site are paid affiliate links. A commission never changes whether a supplier is listed or how its signals are marked. See the affiliate disclosure.

Rechecks and corrections

Listings are rechecked when a supplier's documentation changes or when a correction is reported. Every change is recorded on the changelog. Corrections can be sent to info@zvezdaff.com.