Shayer was born at Southampton and after spells at Guildford and Chichester had settled permanently in his native city by 1820. He is principally known for his Hampshire landscapes and animal painting and his work is most closely associated with the New Forest. His work falls into two main categories: woodland scenes, populated with gypsies, animals and cheerful rustics and coastal scenes based around small boats, fishermen and their families.
The death of Shayer's first wife in 1823 left him with five children to raise and made establishing himself as an artist all the more difficult. He was helped by the establishment of the Society of British Artists (with whom he went on to exhibit 388 works) and the opening of the Hampshire Picture Gallery in Southampton in 1827 and by the end of the decade his career was beginning to flourish. He also exhibited at the RA between and 1820 and 1843, and at the British Institution. He was certainly prolific and examples of his work can be found in many provincial museums. Four of his sons are known to have worked as artists the two most successful being William Joseph Shayer (1811 - 1892) and Henry Thring Shayer (1825 - 1894).
William Shayer is represented in the following collections: Fitzwilliam Museum, Cambridge; Tate Gallery, London; amongst others.