Vector vs. Raster Art & File Format Reference
"Never say never!" Yes, there are exceptions to any rule, but, generally speaking, you're safe to to go by my NEVER's and ALWAYS's.
Download a print-friendly PDF here.
Never Vector
.jpg
.png
.psd*
.tif
.gif
.bmp
Raster art will always pixelate at some percentage enlargement.
(depending on it’s size and resolution.)
*PSD files have been expanded to handle vector elements, but, it’s a little complicated. Keep things simple and avoid this for vector art.
May Be Vector
.eps
.ai
.svg
.pdf
Vector art MUST be one of these formats.
BUT, confusingly, raster art can also be saved as any of these.
To check if something is truly vector, zoom in close - if you see pixelation at all, it's not vector.
Vector art will never pixelate at any percentage enlargement.
(It is not based on resolution at all.)