In printing, bleed is printing that goes beyond the edge of the sheet before trimming. In other words, the bleed is the area to be trimmed off. The bleed is the part on the side of a document that gives the printer a small amount of space to account for movement of the paper, and design inconsistencies. Artwork and background colors can extend into the bleed area. After trimming, the bleed ensures that no unprinted edges occur in the final trimmed document.
It is very difficult to print exactly to the edge of a sheet of paper/card so, to achieve this, it is necessary to print a slightly larger area than is needed and then trim the paper/card down to the required finished size. Images, background images and fills which are intended to extend to the edge of the page must be extended beyond the trim line to give a bleed.
Bleeds in the US generally are 1/8 of an inch from where the cut is to be made. Bleeds in the UK and Europe generally are 2 to 5mm from where the cut is to be made. This can vary from one print company to another. Some printers ask for specific sizes; most of these companies place the specific demands on their website or offer templates that are already set to their required bleed settings.
Bleed information refers to elements outside the finished piece. Often a printer requires bleed information on pieces that have bleed to allow for "printer bounce" when cutting a job down to size. Failing to provide bleed information and crop marks can result in finished pieces showing a thin area of white on the edge.
Die-cuts sometimes require a 1/4" bleed from where the page is intended to be cut; this is because of the possible movement of the paper during the die-cut procedure.
Full bleed is printing from one edge of the paper to the other without the standard borders by which most personal printers are limited. This is useful for printing brochures, posters, and other marketing materials. Often the paper is trimmed after printing to ensure the ink runs fully to the edge and does not stop short of it.