What Is a Certificate of Analysis (COA)?

A Certificate of Analysis, usually shortened to COA, is a lab report for one specific batch of a product. It's the closest thing to independent proof that what's on the label matches what's actually in the bottle.

What a COA actually tests

A thorough COA covers two different things, and it's worth checking for both:

• Cannabinoid potency — how much CBD, CBG, THC, and other cannabinoids the batch actually contains, tested against what the label claims. This is what confirms the mg count on the bottle is real.
• Contaminant screening — pesticides, heavy metals (lead, arsenic, mercury, cadmium), residual solvents (if the extraction process uses any), and microbial/mold testing. Potency alone doesn't tell you a product is clean; this is the part that does.

Why "third-party" and "independent" matter

A COA is only as trustworthy as the lab that produced it. Look for testing done by a lab with no ownership or financial ties to the brand — an in-house or affiliated lab grading its own company's product isn't an independent check, whatever the paperwork looks like. Reputable brands are usually upfront about which lab did the testing.

Matching the batch number

Cannabinoid content can vary batch to batch, since it depends on the hemp harvest that went into it. A COA is only meaningful for the exact batch it was tested on — most brands print a batch or lot number on the packaging, and some link a QR code straight to that batch's COA. A single COA posted sitewide with no batch number attached is a weaker signal than one that's traceable to what's actually in your hand.

Red flags

• No COA available anywhere on the brand's site.
• A COA that only shows potency and skips contaminant screening entirely.
• A COA with no batch number, or one that's clearly outdated relative to current stock.
• Testing done by a lab that's owned by, or unclear about its relationship to, the brand.

We haven't independently lab-tested any product listed on this site — see our legal page for what that means. This guide is meant to help you evaluate a brand's own claims yourself, not a substitute for reading the actual COA.