Flip over almost any piece of clothing and you’ll find a little tag full of words like polyester, viscose, elastane or modal. Most of us glance at it, maybe check the size, and move on. But those words tell you a lot: how the garment will feel, how it will wear, how to wash it, and how much it cost the planet to make.

This guide walks through the fabrics you’re most likely to see on a tag, what each one is actually made from, and how it stacks up environmentally.

First, how to read the tag

A fiber content label lists each fiber by percentage, largest first, for example 60% cotton, 35% polyester, 5% elastane. Every fiber falls into one of three families:

• Natural fibers come straight from plants (cotton, linen) or animals (wool, silk).
• Semi-synthetic fibers start as something natural, usually wood pulp, but are dissolved in chemicals and re-formed into a new fiber. Rayon, viscose, modal and lyocell are all in this group.
• Synthetic fibers are made from petroleum (oil and gas). Think polyester, nylon, acrylic and elastane. Put simply, they’re plastic.

How we’re rating them

No fabric is perfect. Every one uses land, water, energy or chemicals somewhere along the way. So instead of “good” and “bad,” we’ve sorted them into three groups:

• Better choice: lower impact overall, often biodegradable or made with cleaner processes.
• It depends: can be fine or quite harmful depending on how it was farmed or made.
• Higher impact: made from fossil fuels, heavily polluting to produce, or very hard to break down.

One thing matters more than any of these ratings: how long a garment is worn. A polyester jacket worn for ten years can have a smaller footprint than a cotton tee worn twice. We’ll come back to that at the end.

Natural fibers from plants

Cotton

What it is: the soft, fluffy fiber around the seeds of the cotton plant.

Cotton is breathable, comfortable and biodegradable, and it’s the most common natural fiber in our closets. The catch is how it’s grown. Conventional cotton is a thirsty crop, often irrigated in dry regions, and it relies heavily on pesticides and synthetic fertilizers.

Look for: organic cotton (grown without synthetic pesticides) or recycled cotton. Both are a clear step up.

Linen (flax)

What it is: fiber from the stalk of the flax plant.

Flax grows well with little water and few chemicals, often on rain alone, and nearly the whole plant gets used. Linen is strong, gets softer with every wash, and biodegrades. It wrinkles easily, but that’s part of its charm.

Hemp

What it is: fiber from the stalk of the hemp plant (a cousin of cannabis, without the high).

Hemp grows fast and dense, needs little water, naturally crowds out weeds, and rarely needs pesticides. The fabric is tough, breathable and long-lasting, and modern hemp blends are much softer than the scratchy hemp of the past.

Ramie

What it is: fiber from the stalk of a nettle-family plant, mostly grown in Asia.

You’ll see it on tags less often. It’s similar to linen: strong, crisp, low-input to grow and biodegradable.

Natural fibers from animals

Wool

What it is: hair sheared from sheep. Merino is a fine, soft type of wool from merino sheep; lambswool comes from a lamb’s first shearing.

Wool is warm, naturally odor-resistant, needs washing less often, lasts for years and biodegrades. On the downside, sheep need a lot of grazing land and release methane, a potent greenhouse gas, and animal welfare practices vary.

Look for: certifications such as the Responsible Wool Standard (RWS), or recycled wool.

Cashmere

What it is: the very fine undercoat combed from cashmere goats, mainly raised in Mongolia and China.

It’s luxuriously soft, but each goat produces only a small amount per year, and booming demand has led to overgrazing that damages grasslands. Because it’s so precious, cashmere is one of the best things to buy secondhand. Good cashmere lasts for decades with care.

Alpaca and mohair

What they are: alpaca comes from alpacas in South America; mohair comes from Angora goats.

Alpacas are relatively easy on the land, with soft padded feet and efficient grazing. Mohair has faced animal-welfare concerns, so look for certified sources.

Silk

What it is: the protein fiber silkworms spin to make their cocoons.

Silk is natural and biodegradable, but turning cocoons into fabric takes a lot of energy and water, and conventional silk production kills the silkworm. Peace silk (or ahimsa silk) lets the moth leave the cocoon first.

Leather

What it is: animal hide, usually cow, that has been tanned to stop it from rotting.

Leather is durable and can last a lifetime, but it’s tied to cattle farming, and most leather is tanned with chromium, which can pollute water near tanneries. Vegetable-tanned leather avoids that, and secondhand leather gives an existing hide a longer life.

Semi-synthetics: made from trees, reshaped by chemistry

These fibers start as wood pulp (from trees like eucalyptus, beech, pine or bamboo). The pulp is dissolved into a thick liquid, pushed through tiny holes like a showerhead, and hardened into long threads. The big environmental question is what happens to the chemicals used along the way, and where the trees came from.

Rayon and viscose

What they are: the same thing. Rayon is the general name used in the US; viscose is the most common way of making it, and the name often used on tags.

Viscose drapes beautifully and feels silky, which is why it’s everywhere in dresses and blouses. But the traditional process uses toxic chemicals, including carbon disulfide, that can harm factory workers and pollute nearby air and water. Some viscose is also linked to cutting down ancient and endangered forests. Viscose itself does biodegrade, which is a point in its favor.

Look for: LENZING™ ECOVERO™ viscose or FSC-certified wood sources, which are made with cleaner processes and responsibly sourced wood.

Bamboo

This one surprises people. Bamboo the plant grows fast with little water. But almost every soft “bamboo” fabric is actually bamboo viscose, made with the same chemical process as regular viscose. That’s why labels are often required to say rayon from bamboo or viscose from bamboo. The plant is green; the process usually isn’t.

Modal

What it is: a type of rayon usually made from beech trees, known for being extra soft and holding its shape. Many brands, especially LENZING™ Modal, use cleaner production than standard viscose.

Lyocell (TENCEL™)

What it is: a newer type of fiber made from wood pulp, usually eucalyptus. TENCEL™ is the best-known brand name.

Lyocell uses a non-toxic solvent in a closed loop, meaning almost all of it is captured and reused instead of being dumped. The result is soft, breathable, strong and biodegradable. It’s one of the best options among manufactured fibers.

Cupro

What it is: a silky fiber made from cotton linter, the tiny fuzz left on cotton seeds that’s usually thrown away. Using waste is a plus, but production involves copper and ammonia, so how well the factory handles its chemicals makes a big difference.

Acetate

What it is: a shiny fiber made from wood pulp treated with acetic acid, common in linings and evening wear. It’s made with heavy chemical processing and breaks down slowly.

Synthetics: plastic you can wear

Synthetic fibers are made from oil and gas. They’re cheap, strong, and often stretchy or water-resistant. But making them burns fossil fuels, they don’t biodegrade in any meaningful timeframe, and every wash sheds tiny plastic microfibers that flow down the drain and into rivers and oceans.

Polyester

What it is: a plastic, the same family as the plastic in drink bottles (PET).

Polyester is the most-used fiber in the world, making up more than half of all fiber produced. It’s durable, wrinkle-resistant and quick-drying, which is why it’s in everything from fleece to dresses. It takes roughly 200 years or more to break down and sheds microplastics with every wash.

Recycled polyester (rPET) is usually made from plastic bottles. It cuts down on new oil use, but it still sheds microfibers, and once a bottle becomes a shirt it’s rarely recycled again.

Nylon (polyamide)

What it is: a strong, smooth plastic fiber, used in tights, activewear, swimwear and outerwear. Polyamide is just another name for nylon.

Making nylon is energy-intensive and releases nitrous oxide, a powerful greenhouse gas. Recycled nylon, such as ECONYL®, made from old fishing nets and carpet, is a much better alternative.

Acrylic

What it is: a plastic fiber designed to imitate wool, very common in cheap sweaters, hats and scarves.

Acrylic is often rated one of the least sustainable fibers. It’s made from fossil fuels using hazardous chemicals, it pills quickly (so it tends to be thrown out sooner), and studies have found it sheds more microfibers in the wash than polyester. If a “wool” sweater feels surprisingly cheap and squeaky, check the tag.

Elastane (spandex, Lycra®)

What it is: a super-stretchy plastic fiber. Elastane, spandex and the brand name Lycra® all mean the same thing.

You’ll usually see just 2–10% of it, adding stretch to jeans, leggings and T-shirts. It’s petroleum-based and doesn’t biodegrade, but its biggest problem is that even a little elastane makes a garment nearly impossible to recycle, because the fibers can’t easily be separated.

Polypropylene

What it is: a lightweight plastic fiber used in thermal base layers and some sportswear. Fossil-fuel based, but very light and long-lasting.

Faux leather (PU and PVC)

What it is: fabric coated in plastic, either polyurethane (PU) or polyvinyl chloride (PVC). Often sold as vegan leather.

It avoids animal products, but it’s still plastic, tends to crack and peel within a few years, and PVC in particular involves harmful chemicals. Newer plant-based alternatives, made from things like cactus, mushroom or apple waste, are promising, though many still include a plastic backing.

Quick reference: what’s on the tag

A word about blends

A tag like 55% cotton, 40% polyester, 5% elastane is very common, and blends do have benefits: more stretch, fewer wrinkles, better durability. But mixing fibers makes a garment very hard to recycle, because the fibers can’t easily be pulled apart. A single-fiber garment (100% cotton, 100% wool) has a much better chance of being recycled at the end of its life.

Making synthetics less harmful

You don’t need to throw out anything with polyester in it. If you own synthetics, a few habits help:

• Wash less often, in cold water, with full loads. Fewer washes means fewer microfibers.
• Use a microfiber-catching wash bag or filter, such as a Guppyfriend bag.
• Air-dry instead of tumble-drying.
• Keep wearing it. The longer a garment stays in use, the less its manufacturing cost matters.

The bottom line: the greenest fabric is the one already made

Every fabric on this list took land, water, energy or oil to produce. Once a garment exists, that cost has already been paid. Buying secondhand means no new fiber is grown, spun, dyed or shipped, and that’s true whether the tag says organic linen or polyester.

So here’s our advice: when you buy new, use the tag to choose wisely. And whenever you can, choose secondhand first. Bring us the pieces you’ve loved, and find your next favorite in someone else’s closet.

Have a question about a fabric we didn’t cover? Ask us in the store or leave a comment below. We’ll add it to the guide.