What is 'resolution'? What resolution should my image/photo be for uploading?

Resolution is the degree of detail visible in a raster or vector image.

Raster images (like photos) are comprised of pixels — or, dots of colour.

• High resolution means there are many dots per inch.
• Low resolution means fewer dots per inch, and poorer quality.
• For VistaPrint products, aim for at least 300 dpi at the desired image size unless the product indicates otherwise.

Vector images are not comprised of pixels; they're calculated and displayed with the help of mathematical equations.

• They can be stretched to any size while maintaining high quality.
• It's preferable to use vector images whenever possible.