What Is a DST File? A Practical Guide to Tajima Embroidery Files

If you've worked with embroidery machines, you've almost certainly come across a .dst file. DST — short for Data Stitch Tajima — is the format originally used by Tajima commercial embroidery machines, and it has become one of the most widely supported machine formats in the industry.

While building EmbroidAI, we spent a lot of time inside DST files. This guide explains what they contain and why they behave the way they do.

A DST file is a list of movements, not a picture

Unlike an image or a vector file, a DST file doesn't describe what a design looks like. It describes how the machine should move. The file is essentially a sequence of instructions:

• move the needle by a certain amount and make a stitch,
• move without stitching (a jump),
• stop for a colour change, and
• end the design.

Every visual property of the finished embroidery — fills, satin columns, outlines — emerges from thousands of these small movements.

The structure of a DST file

A DST file has two parts.

1. A 512-byte header

The header is plain ASCII text padded to 512 bytes. It includes fields such as:

Field	Meaning
LA	Design label (name)
ST	Number of stitches
CO	Number of colour changes
+X, -X, +Y, -Y	Extents of the design from the start point
AX, AY, MX, MY, PD	Positioning and multi-design information

The extents let software and machines know the design's size before reading any stitch data.

2. Stitch records

After the header, the body is a series of 3-byte records. Each record encodes:

• a relative X movement,
• a relative Y movement, and
• flags describing what kind of movement it is (normal stitch, jump or colour change).

Movements are stored relative to the previous position in units of 0.1 mm, and a single record can move at most 12.1 mm in each direction. Longer movements are split into several consecutive jump records. The file ends with a special end-of-design record.

Why DST files don't have colours

One of the most common surprises: DST files don't store thread colours. A colour change record only tells the machine to stop so the next thread can be used. Which thread goes on which needle is decided by the machine operator or by a separate colour sheet.

That's why the same DST file can look completely different in two viewers — each one guesses colours using its own default palette.

What you can learn from analysing a DST file

Because the format is so explicit, a lot can be computed directly from the stitch data:

• Stitch count — a key input for pricing and production time.
• Number of colour stops — how many thread changes the design needs.
• Dimensions — the real-world size of the design.
• Jumps and trims — long jumps can indicate areas that need trimming.
• Density — clusters of short stitches can reveal areas that may pucker or break thread.

This is exactly the kind of analysis EmbroidAI performs in the browser, alongside a stitch-by-stitch simulation so you can see how a design will sew out before it reaches the machine.

Key takeaways

• DST is a machine format: it stores movements, not images.
• The file is a 512-byte header followed by 3-byte stitch records.
• Movements are relative, in 0.1 mm units, with a maximum of 12.1 mm per record.
• Thread colours are not stored — only colour-change stops.

Curious how AI can help with embroidery workflows? Explore EmbroidAI.