What is a vector file?

Shapes versus pixels

A raster file — PNG, JPG, WebP, BMP, GIF — is a grid. Each cell holds a colour, and the picture is the arrangement of cells. Enlarge it and there is nothing between the cells to show, so the software either repeats them or blurs between them. Both look wrong.

A vector file stores geometry: this path goes from here to there curving like this, and it is filled with that colour. Nothing is decided about resolution until something draws it. Ask for it at 40 mm or at four metres and it is computed fresh at that size, so the edges are exactly as sharp either way.

What that buys you

Scaling without loss is the headline, but it is rarely the reason a professional needs one. The practical reasons are these: a cutter, plotter or engraver needs a path to follow, and a grid of pixels is not a path. A print RIP separates colours per shape. An editor can select and move an individual outline. A file can be recoloured for a one-colour application without re-drawing it.

The size property is a side effect worth knowing anyway. A logo as vector is often a few kilobytes because it is a description of a dozen shapes. The same logo as a print-resolution raster is megabytes, because it is every pixel of a large grid.

Which formats are vector

SVG is the web-native one: XML, human-readable, opens in every browser and every editor. It is the right default for anything that will be edited or shown on screen.

PDF is a page description that carries vector content, plus a page size and print metadata. It is the format nobody can fail to open, which makes it the safest thing to email.

EPS is Encapsulated PostScript, the pre-press interchange format. It is old and it persists because RIPs, screen printers and sign shops built their workflows on it and never needed to move.

DXF is AutoCAD Drawing Interchange: geometry, layers and real drawing units, with no fills at all. It is what cutters, routers and plasma tables read, because a machine needs a toolpath, not artwork.

AI and CDR are the native formats of Illustrator and CorelDRAW. They are vector and they are also application files; send one only to someone you know has the application.

The fake vector file

All four of the interchange formats above can embed a bitmap. An SVG can hold a base64 PNG, an EPS can hold a raster image, a PDF can be a scan. The container says vector and the contents are pixels, and every property people wanted from a vector file is missing.

This is the single most common reason a print shop rejects a file. The fix is not a different exporter, it is tracing: something has to look at the pixels and decide where the shapes are.

To check a file you have been given, open it and zoom to 800%. Crisp edges mean geometry; a stepped edge means pixels. In an editor, click an edge — a real vector file selects a path with nodes on it.

When you do not need one

Photographs. A photograph has no flat regions and no crisp boundaries; converting it to vector produces a posterisation, which is a stylistic choice rather than a conversion. Keep photographs raster.

Screenshots and UI captures, for the same reason plus one more: they contain rendered text, and traced text is outlines that cannot be re-typed.

Anything that is only ever displayed at one size on a screen. A vector file is not automatically better; it is better when something downstream needs shapes.

Getting one when you were not given one

Ask first. Almost every logo was vector once, and whoever designed it may still have the file. Five minutes of email beats an hour of tracing and a result that is only close.

If the original is gone, trace what you have. A good trace of a clean, reasonably large PNG is very close to the original for print, cutting and resizing, and it is a large improvement over upscaling. It does not recover the original curve construction, and it will not reproduce a typeface exactly — so for a mark that will be reused for years, treat the trace as a working file and get the real one when you can.