The inscriptions, apparently composed by the priests of Memphis, summarize benefactions conferred by Ptolemy V Epiphanes (205–180 BC) and were written in the ninth year of his reign in commemoration of his accession to the throne. Inscribed in two languages, Egyptian and Greek, and three writing systems, hieroglyphics, demotic script (a cursive form of Egyptian hieroglyphics), and the Greek alphabet, it provided a key to the translation of Egyptian hieroglyphic writing.

The decipherment was largely the work of Thomas Young (Young, Thomas) of England and Jean-François Champollion (Champollion, Jean-François) of France. The hieroglyphic text on the Rosetta Stone contains six identical cartouches (oval figures enclosing hieroglyphs). Young deciphered the cartouche as the name of Ptolemy and proved a long-held assumption that the cartouches found in other inscriptions were the names of royalty. By examining the direction in which the bird and animal characters faced, Young also discovered the way in which hieroglyphic signs were to be read.

In 1821–22 Champollion, starting where Young left off, began to publish papers on the decipherment of hieratic and hieroglyphic writing based on study of the Rosetta Stone and eventually established an entire list of signs with their Greek equivalents. He was the first Egyptologist to realize that some of the signs were alphabetic, some syllabic, and some determinative, standing for the whole idea or object previously expressed. He also established that the hieroglyphic text of the Rosetta Stone was a translation from the Greek, not, as had been thought, the reverse. The work of these two men established the basis for the translation of all future Egyptian hieroglyphic texts.