Is COS sustainable? We checked 837 products.

On fabric composition — the one factor we can measure — COS averages 77.6% natural fibre across 837 products, ranking #13 of 55 brands we track. That's among the better scores. Fabric data can't speak to labor practices, emissions, or water use, so treat this as one input, not a verdict.

We measure fabric, not business models — so we can't classify COS as fast fashion or not. What the data shows: 9.3% of their products are polyester-heavy and 54.5% are nearly all-natural (95%+ natural fibre). Heavy synthetic reliance often correlates with fast-fashion production, but it isn't proof either way.

Fabric composition is a reasonable quality proxy: natural fibres generally breathe better, last longer, and shed fewer microplastics. COS averages 77.6% natural fibre, which is better than most brands we track. Individual items vary widely, so check the composition label on each piece.

That depends on what you're buying. 54.5% of COS's catalog is nearly all-natural, so good pieces exist even beyond their solid average. Use the Fibr extension to check fabric composition on individual items while you shop — it varies more within a brand than between brands.

18.2% of COS products are majority synthetic (less than 50% natural fibre by weighted content). The catalog as a whole averages 77.6% natural fibre, so it leans natural.