Hornby played for the youth teams at Hednesford Town and Redditch United before turning professional after signing a one-year contract with Jimmy Floyd Hasselbaink's Burton Albion in June 2015.
[4] He joined National League North side Brackley Town on an initial one-month loan in October 2015, and went on to remain an ever-present for the rest of the 2015–16 season as the "Saints" successfully avoided relegation.
[10] He made his debut for the "Valiants" in the first round of the EFL Cup on 9 August, coming on for Lainton – who had suffered a serious thigh injury – at half-time during a 4–1 defeat to Leeds United at Elland Road.
[26] He moved on loan to AFC Fylde on 7 October after manager Gary Bowyer wanted Hornby to play regular football rather than sit on the bench as cover for Richard O'Donnell.
[27] Dave Challinor stated that he brought Hornby to the "Coasters" after goalkeepers James Montgomery and Dan Lavercombe suffered a loss of confidence following Fylde's record of 29 goals conceded in the opening 15 games of the National League season.
[28] Hornby played 21 games in the 2020–21 season, which proved a difficult campaign for the club and one which he described as "a real mixed bag and a test of character" after he replaced an injured Richard O'Donnell in the starting eleven.
[29] Joint-managers Mark Trueman and Conor Sellars signed Will Huffer from Bradford (Park Avenue) in January to provide back-up for Hornby rather than attempting to bring in an experienced goalkeeper to replace him in the starting line-up.
[33] Having featured nine times for Bradford during the first half of the campaign, he joined League Two rivals Colchester United on loan until the end of the 2021–22 season on 31 January 2022; "U's" manager Wayne Brown required goalkeeper cover following suspension to Shamal George, injury concerns with Dean Gerken and the inexperience of Ted Collins.
[34] He made a good impression at the Colchester Community Stadium, being named in the League Two Team of the Week for the final of his eight appearances, leading to speculation that he would be a summer transfer target.
[48][49] On 24 July 2024, Hornby joined Walsall on a permanent one-year deal having impressed on his trial period; he had previously spent time with the club's academy before his departure aged 14.