Mylar bags are flexible pouches made from a metallized polyester film, often layered with foil and other films. That layered structure blocks light, oxygen, and moisture, which is the whole point: the barrier is why mylar keeps coffee, food, edibles, and other sensitive products fresh, smell proof, and shelf stable.
What mylar actually is
Mylar is a brand name that became the common term for a strong, thin polyester film. For packaging it is usually combined with a metallized or foil layer and a sealable inner layer, so the finished bag prints well on the outside, seals shut, and forms a barrier in the middle.
Why the barrier matters
Light, air, and humidity are what stale out food and degrade products. A good mylar bag slows all three, which extends shelf life and locks in aroma. That is why it is the default for coffee, snacks, supplements, and anything scent sensitive.
Common mylar bag styles
The main formats are the stand up pouch with a bottom gusset, the flat pouch, the resealable ziplock bag, and die cut or custom shapes with a window. Sizes run from small single serve up to bulk storage. See our custom mylar bags range and the full mylar bags category, all no minimum order.
More packaging explainers: rigid boxes, corrugated cardboard, kraft paper, dielines.