Custom Printed Mylar Bags with a Window for UK Food Brands

What is a mylar bag with a window?

A mylar bag with a window is a foil or metallised laminate pouch where part of the front panel is left clear. The bag in our photo is matte black with a vertical strip down the right hand side, a zipper under the tear notch and a gusset at the base.

The window is not a hole with film glued over it. The pouch is made from a laminate that has a clear PET outer, and the metallised or foil layer is simply left out where the window sits. That keeps the seals continuous and the bag one piece.

You lose a little barrier through the window area. For most dry snacks and sweets that matters less than the sale the window helps you make. Our range of foil mylar bags covers the fully opaque versions if you need them.

Which products sell better with a window?

Anything that looks good in the bag. A granola brand in Bristol wants the clusters and freeze-dried raspberries visible. A pick and mix seller wants the colours on show. A pet treat maker wants the owner to see the size of the biscuit.

The window also helps where shoppers are wary of a new brand. Seeing the product settles the question of what is inside and how much of it there is.

• Granola, muesli and oat clusters with visible fruit
• Dried fruit, nuts and roasted seeds
• Fudge, bonbons and boiled sweets
• Pasta shapes, lentils and rice
• Bath salts, bath tea and soap flakes
• Dog biscuits and dental chews

What window shapes can you print around?

A straight strip down one edge is the cleanest option and the easiest to fill around. A rectangle or oval in the centre of the front panel gives a framed look. Circles suit round products such as bonbons.

Shaped windows cut from your artwork are possible too: a leaf for a tea blender, a paw for a pet brand, a bone for dog treats. Keep any shape at least 10 mm inside the side seals so the seal bars never cross the window edge.

Frosted windows soften the view and hide small differences between batches. Clear windows show the product exactly as it is. Our guide on designing artwork for printed pouches explains how to mark the window on your file.

How do I size a window bag by fill weight?

Start with the fill weight and how dense the product is. Granola at 250 g needs more room than 250 g of boiled sweets, because the clusters trap air between them.

Allow 30 to 40 mm of empty film above the fill line for the zipper and the top seal. Then decide where the window should sit. A window that runs below the fill line shows empty bag, which looks like short measure to the shopper.

Tell us the product, the fill weight and the window position you have in mind. We size the pouch and move the window so it sits over the full part of the bag, then show you the result on the free proof.

Laminate and barrier around the window

The opaque area of the bag is usually metallised PET / PE for a matte black or printed look, or PET / foil / PE where the product is oily or needs a longer shelf life. Kraft / PET / PE works with a window as well, giving a brown paper outer with a clear slot.

The window itself is clear PET / PE, so light and a small amount of oxygen pass through it. Keep windows modest on nut products and anything with a high oil content, as light speeds up rancidity. Food-contact, high-barrier and compostable film options are available on request and confirmed on the quote.

If you are unsure how much window your product can tolerate, read our guide to barrier films and laminates explained before you decide.

Zipper, tear notch and gusset

Window bags normally have a press-to-close zipper 20 to 25 mm below the top seal and a tear notch on each side above it. The customer tears across, opens the zipper and reseals after each use. A slider zipper is available on request for bags above 500 g where a grip helps.

The bottom gusset folds flat for shipping and opens as the bag fills, so the pouch stands upright on a shelf. A deeper gusset gives a fatter bag and a shorter front, which can push the window lower than you planned. We check this on the dieline. Many of the same choices apply to our stand up pouches with a clear window in lighter laminates.

Print and artwork on a window bag

Everything outside the window prints as normal: plain, one colour, two colour, full colour digital or full colour plate print. White under-print sits beneath the colours on metallised and foil films so they do not go dull.

The window area needs to be marked on your artwork as a clear zone with no ink. A thin printed keyline around the window hides any tiny shift between the print and the clear area, and it looks neat. Matte, gloss, soft touch matte and spot gloss over matte finishes all work with a window.

Send your logo through Design Your Pouch on this site and our designers build the layout around the window for free.

How do I fill and seal a window bag?

The sequence below suits a small team filling by hand or with a bench top heat sealer. The window makes it easy to spot a bag that was filled short before it reaches a customer.

1. Open the gusset with a finger so the bag stands on its own.
2. Fill through the top using a scoop or a funnel, keeping product out of the zipper channel.
3. Tap the bag on the bench so the product settles below the zipper.
4. Wipe the inside of the top seal area if any dust landed there.
5. Press the zipper shut from one side to the other, then heat seal the top above it.
6. Check the window shows a full bag and the seal is flat with no wrinkles.

What mistakes do people make with window bags?

The first is a window that drops below the fill line. The bag looks half empty even when the weight is right. Tell us the fill weight so we can position the window.

The second is a window too close to the seal edge. The seal bar crushes the clear film and the edge looks ragged. We keep at least 10 mm of margin on the dieline.

The third is choosing a big clear window for an oily product with a long shelf life. Light gets in and the product fades or goes rancid before the best before date. A smaller window or a frosted one is the safer choice. The same thinking applies to our printed pouches for snack brands.

How do I order mylar bags with a window?

Send the product name, the fill weight, the window shape you want and your artwork or logo. Quantities are quoted per order, from £0.25 per unit, and the figure is confirmed on a written quote.

You get a free design proof showing the window position before anything is printed. After approval, production takes 4–6 business days and your bags arrive free with tracking anywhere in the UK in 2–3 business days.

Misprints or damage reported within 10 days with photos are reprinted or refunded. Use the quote request form for printed pouches or message us on WhatsApp with a photo of your product.