Packaging dielines: a plain-English guide

A dieline is the blueprint of a piece of packaging — the flat shape that gets cut, creased and folded into the finished box, carton or sleeve. If you've ever wondered why packaging artwork comes back with strange coloured lines on it, this is for you.

What a dieline actually is

A dieline is a vector template, supplied by the printer (or the structural designer), showing the exact shape of the unfolded packaging. It tells the press where to:

• Cut the substrate
• Crease it so it folds cleanly
• Perforate for tear strips and feature openings
• Glue the panels together

Every box, carton, label, sleeve, pouch and clamshell has its own dieline. They're not interchangeable — even two cartons that look identical from the outside will have subtly different dielines depending on the press and the substrate.

Why you can't invent one

Designers sometimes build a "rough dieline" from measuring a flat sample. It almost always ends badly.

Real dielines account for:

• The substrate thickness (carton vs corrugated changes flap allowances)
• The press the job will run on
• The folding line tolerances
• The glue tab geometry
• The crease bleed (paper stretches when you crease it)

A rough dieline that looks right on screen will fold wonky on press. Always get the real one from the printer before artwork starts.

What the coloured lines mean

There's no universal standard, but most printers use something close to this convention. They'll usually supply a key.

• Black or magenta solid line — cut line (the blade)
• Blue dashed line — crease / fold line
• Green dotted line — perforation
• Red dashed line — reverse fold (folds the other way)
• Yellow fill — glue tab area (don't put artwork here)
• Cyan dashed line — safe area (keep critical copy inside)

The exact colours vary by printer. Always read the legend they supply with the file.

Setting up dieline layers properly

The dieline lives on its own layer, named clearly, and set to non-printing. In Illustrator, that means:

1. Create a layer called Dieline (or Cutter)
2. Set all dieline strokes to a named spot colour, often called Dieline or Cutter
3. Set every dieline element to Overprint Stroke
4. Set the layer to non-printing in the PDF export

When the printer's RIP processes the file, the spot colour separation drives the cutting plotter — and the artwork prints underneath without interference.

Bleed across the dieline

Every cut edge needs bleed. Every fold needs bleed. Every perforation needs bleed.

The reason: presses register to about ±0.3 mm, and cutters register to about ±0.5 mm. Without bleed, any drift between print and cut leaves a white line at the edge of your panel.

Typical bleed for cartons:

• Folding cartons — 3 mm past every cut and crease
• Corrugated cases — 5 mm
• Labels — 2–3 mm (depending on die accuracy)

Safe area: keep clear

Critical copy and logos should sit well inside the cut and fold lines. Folds in particular pull copy out of shape — a logo placed too close to a fold can end up with its top half on the front panel and its bottom half wrapped around the side.

Rule of thumb: keep critical artwork at least 3–5 mm clear of every cut, fold and perforation.

A pre-flight checklist for dielines

Before you send the file:

• Dieline is on its own non-printing layer, named clearly
• Dieline strokes are set to a named spot colour, overprint on
• Bleed extends past every cut, fold and perforation
• Glue tabs are clear of artwork
• Safe area is respected on every panel
• Folded panels read the right way up when the carton is assembled

That last one trips people up more than anything else. Always mock the carton up — physically — before delivery.

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Need packaging artwork built to a real printer's dieline, with the bleed and folding handled properly? Get in touch — files that fold clean, first time.