Vector or bitmap, and why it decides how a logo prints
Vector artwork is stored as drawing instructions: coordinates, curves and fills that a printer works out at whatever size it is asked for. A bitmap is stored as a fixed grid of pixels, so enlarging it past its natural size spreads those pixels thinner and softens every edge.
That is the whole difference, and it is why a printer asking for "a vector file" is not being awkward. The same logo can be printed on a business card and on the side of a van from one vector file. From a bitmap it can be printed once, at one size, and anything larger looks worse.
How to tell what you have
Two checks need no special software, and a third is what this site automates.
- Zoom in hard. Open the file and magnify to 1600 percent or more. Vector edges stay clean at any magnification. A bitmap breaks into visible squares.
- Try to select one part. In Illustrator or Inkscape, genuine vector artwork lets you click individual shapes. If the whole logo selects as a single rectangular object, it is a placed bitmap.
- Read the drawing instructions. That is what the checker here does: it counts how much of the visible artwork is made of drawing instructions rather than placed images, and then magnifies the file so you can confirm the answer instead of taking its word for it.
The formats, one by one
A container, not a promise. A PDF is a page description, and a page can describe anything: curves and fills, live text, a placed photograph, or a scan straight off a copier. All four are valid PDFs and all four open identically in a viewer. A PDF holding one enormous JPEG prints exactly as badly as the JPEG would.
SVG
Plain XML, and the easiest format to inspect by hand. It is also the easiest to be fooled by, because SVG has an image element: a file can consist of one base64 encoded PNG and nothing else, and still be a completely valid SVG. Open it in a text editor rather than a viewer. A long run of characters after data:image/png;base64 means there is a bitmap inside it. Many path elements full of coordinates mean real drawn artwork.
AI
Illustrator's own format. Modern versions are PDF underneath, which is why a .ai file often opens in a PDF reader. Older ones, before Creative Suite, are raw PostScript. Either way the format guarantees nothing about the contents: an Illustrator file can hold a single placed photograph just as easily as drawn artwork.
EPS
The hardest to be certain about, because PostScript is a programming language rather than a description of a page. An EPS is a program that draws one, and a file can compute artwork while it runs that appears nowhere in its text. Reading the instructions without executing them is the honest way to inspect an untrusted file, and it is right about ordinary artwork, but it is why an EPS verdict here says almost certainly rather than yes.
EPS has two traps of its own. Many carry a small TIFF or WMF preview thumbnail in a binary header so layout software can show something without interpreting the PostScript. That preview is a bitmap and it is not the artwork, so a checker that scans the whole file for image data condemns perfectly good vector logos. And a DCS file splits into one file per printing plate, leaving a master that points at the others: send only the master and the colour comes out wrong.
PNG, JPEG, GIF, WebP, TIFF and BMP
Always bitmaps, without exception. There is no version of these formats that holds drawing instructions. Renaming one to .eps or .svg converts nothing, because print software goes by the contents rather than the name, and a mismatch like that is reported here as a finding in its own right.
The fake that catches people out
The single most common bad file in print is a bitmap in a vector wrapper: someone opened a PNG, placed it on a page, and saved as PDF, EPS or SVG. The file now has the right extension and is, in every way that matters, still the bitmap it started as.
This is also where most checkers fail. Counting elements is not the same question as asking how much of the visible ink is resolution independent. A file holding one full bleed embedded photograph plus a stray zero-size rectangle left behind by an export does contain a vector element, and a counting tool will happily call it vector artwork. Anything hidden, fully transparent, zero-sized or positioned outside the canvas is excluded here before anything is judged, which is why a file can be reported as a bitmap in disguise even though it technically contains paths.
Resolution, and why prints come out blurry
A bitmap holds a fixed number of pixels. Printing it larger does not create more of them, it spreads the ones you have over more paper, and the measure of how thinly they are spread is dots per inch. An image 500 pixels wide printed 100 mm across works out at about 127 dpi, well under the 300 dpi commercial printing generally expects.
The usual advice of 300 dpi for everything is right for something held in the hand and wasteful for something read from across a room. Around 150 dpi is normal for posters and exhibition panels, and 100 dpi is fine for banners seen from several metres. Below 100 is too soft for almost any printed use, and usually means the file came off a website rather than from the original artwork. The print size tool works all of this out from the file itself.
Can a PNG or JPEG be converted to vector?
Not by renaming it, and not by re-saving it in a vector format. Exporting a photograph to SVG or EPS wraps the same pixels in a different container, and a checker will still report it as a bitmap. The pixels carry no record of the curves that made them, because that information was destroyed when the image was first rasterised.
Automatic tracing can approximate simple flat shapes, and it usually shows on lettering and fine detail, so it is a last resort rather than a fix. The two routes that genuinely work are asking whoever designed the logo for the original artwork, which normally exists as an Illustrator or SVG file, or having it redrawn properly. Both solve it permanently instead of once.
Live text and fonts
Text in a vector file is still vector, but it depends on the font being available wherever the file is opened. If it is not, the text is silently substituted and the layout shifts, which is a failure that shows up only after something is printed. Converting text to outlines before sending removes the risk entirely, at the cost of no longer being able to edit the wording.
Does this upload my files anywhere?
No. There is no server to upload them to. Every check runs in your browser and the file never leaves your machine, which also means it works on artwork you are not allowed to send to a third party. You do not have to take that on trust: open your browser developer tools, watch the network panel, and drop a file in. Nothing is sent, because the page makes no external request at all. The privacy page sets out exactly what that covers.