How to tell if a file is vector

25 September 2026 · Pathside guides

Pathside opens .ai, .eps, .svg and PDF on the phone →

What makes a file vector rather than raster

A raster image is a grid of coloured squares. A photograph is the obvious case: millions of pixels, each one a fixed colour in a fixed place. Enlarge it and there is no extra detail to find, so the squares simply get bigger.

A vector file stores instructions instead — points, curves, fills, strokes — and the program drawing it works out the pixels fresh at whatever size you asked for. That is why the same logo can sit on a business card and on the side of a van without ever being redrawn.

The practical consequence is the one everybody cares about: a vector can be scaled up indefinitely and stay sharp, while a raster can really only be scaled down. It is also why vector artwork of a logo is usually far smaller on disk than a high-resolution photograph of the same thing.

Which file extensions are vector?

These are the five you are likely to be sent, and what each one really is:

• .ai — Adobe Illustrator. Almost always holds a complete PDF inside it as well, which is why an .ai file opens in a PDF reader.
• .eps — Encapsulated PostScript, the older interchange format. It is a program describing the drawing, not a picture of it.
• .svg — Scalable Vector Graphics, an XML format that every modern browser draws. .svgz is the same thing, gzipped.
• .pdf — can be vector, raster, or both in one page. See below.
• .cdr — CorelDRAW's own format. Vector, but proprietary: up to X3 it was a RIFF container, and from X4 it is a zip archive.

And the ones that are never vector, whatever anybody tells you: .jpg, .png, .gif, .bmp and .tiff. A screenshot of a logo is a raster image of a logo. Placing a JPG inside an Illustrator document does not make the JPG vector either — it makes a vector file with a raster picture sitting in it.

The zoom test, and how to read it

This is the check that settles it, and it needs no software you do not already have.

1. Open the file in something that draws it properly rather than showing a thumbnail.
2. Zoom right into an edge — the curve of a letter, the corner of a shape.
3. If the edge stays a clean line, you are looking at vector. If it breaks into squares, or softens into a smudge, it is raster.

Two honest caveats. A preview thumbnail is always a raster image, so judging by the thumbnail proves nothing. And every viewer has a ceiling: Pathside redraws the page from the vector at the zoom your pinch settles on, up to a budget of eight megapixels — around a three- to four-times pinch on a 1080-pixel-wide phone — and past that it reuses its last render, which softens. So do the test at a moderate zoom, not the deepest one the app allows.

Why the extension can lie

Two different things go wrong here, and they get confused with each other.

The first is renaming. A file called logo.ai may have been a .cdr or a JPEG that someone renamed, and the insides do not change when the name does. This is common enough that Pathside decides what a file is by reading its first bytes rather than trusting the extension — a PDF starts with %PDF, a PostScript file with %!PS, a Photoshop document with 8BPS.

The second is contents. A vector extension accepts raster content: an .eps or a .pdf can be nothing but a scanned photograph wrapped in a vector container. The container is vector; the artwork inside is not. Only looking at it tells you which you have, which is what the zoom test is for.

Is a PDF a vector file?

Sometimes. A PDF page can hold vector paths, live text and raster images at once, so the answer depends entirely on what the program that made it put there. A logo exported from Illustrator is vector. A scan of a printed letterhead is a photograph in a PDF wrapper, and zooming in will show you that immediately.

This matters when a printer asks for “the vector” and you send a PDF. If the PDF came out of drawing software, you have probably given them what they wanted. If it came out of a scanner or a phone camera app, you have given them a picture, and they will probably ask again.

What if what you have is not a vector?

Then nothing turns it back into the original. Tracing software, on a phone or a desktop, can approximate the shapes, and a designer can redraw the artwork properly, but neither recovers the original paths — they make a new file that resembles the old one. Both are worth doing for a logo you will use for years; neither is a five-minute fix on a phone.

The quicker route is usually to go back to whoever sent it. The person who drew the logo has the working file, and asking for “the .ai, the .eps or a PDF straight from Illustrator” is a request they will understand. If you are staring at a CorelDRAW file, the CDR guide covers what to ask for instead, because few programs outside CorelDRAW read that format well.

Checking it when all you have is a phone

Most of these files arrive in a chat app or an email while you are away from a computer, which is where the extension question usually starts. A couple of things are possible from there.

If it is an SVG, it is plain text: opening it in a text editor shows the <svg element and a list of path coordinates, which is about as direct a confirmation as you can get. If it is an .ai or a PDF, you need something that renders it — see how to open an AI file on Android for the way the file usually has to be handed over from WhatsApp or Gmail.

Once it opens, the rest is the zoom test plus whatever you actually needed to check: the right version of the mark, the right wording, the right colourway. Our guide to checking a logo before it goes to print lists the things that get missed, and the one thing a phone screen genuinely cannot judge.

What to do with the answer

If it is vector, keep the file. It is the master, and every size you will ever need comes out of it — which is also when the export size question becomes the next thing to get right.

If it is raster, note what resolution you have before you plan anything around it, and ask for the vector while the person who made it still remembers the job.