Optar (OPTical ARchiver) is a 2D (matrix) barcode. Barcodes are nothing more than a way to store any information (digital data) printed on paper or other material. This code was designed by Twibright Labs, best known for having developed the free space optics link RONJA.
Optar is published as a free software under the GNU General Public License. The intended use is to archive information on paper (film, microfilm, microfiche, ...) in both space efficient way and to protect the user against digital obsolescence.
Optar doesn't aim at maximum data storage density, instead opting for the maximum probability of recovery of the stored information. For this reason even when used with 600dpi laser printers and a typical quality office paper.it switches to only 200dpi resolution to achieve the overall useful data capacity of about 200kB per A4 paper.
Optar uses Golay code to protect the data against errors.