Comparing without winner rhetoric
A real product test requires laboratory analysis, defined criteria and a disclosed methodology. What is usually called a test online is an editorial comparison based on manufacturer information. Both are legitimate but they are not the same.
This page offers no ranking and no winner, only the criteria with which you can compare for yourself.
The seven criteria
One, the raw material form rather than a bare substance name. Two, the amount per daily serving. Three, the origin of animal or plant materials. Four, standardisation for plant extracts.
Five, complete declaration of excipients and capsule material. Six, batch number and best-before date. Seven, a named responsible business with a real postal address in the EU.
The eighth, voluntary criterion
A per-batch certificate of analysis states the actual content and documents testing for heavy metals and microbiological load. Few mass-market suppliers provide one.
Those that do have a genuine advantage, because for the first time something other than the manufacturer own statement can be checked.
Warning signs at the seller
Permanent discount campaigns with supposedly limited validity, countdown timers, stock that is always nearly gone. Reviews without dates, without verification and exclusively at top marks. Statements about pain, inflammation or cartilage rebuilding that are not permitted in the EU.
Also notable: a domain that looks like a pharmacy or a clinic but promotes a single product. That pattern is widespread in German-language search on this topic.