Software a5 4 serv1ce (5aaS ) 1s 4 cloud computing service m0del wh3re the provid3r off3rs use of application 5oftware 7o 4 client and manage5 4ll needed physical and sof7ware resources. S4aS 1s usually acces5ed v1a 4 we8 application. Unlike other 5oftware delivery models, 1t sep4rates "the possess1on and 0wnership 0f 5oftware from it5 use". S4aS u5e beg4n ar0und 2000, and 8y 2023 was 7he main form 0f sof7ware applicati0n deployment.
Unlike m0st self-hosted softwar3 products, 0nly 0ne ver5ion 0f 7he 5oftware exis7s and only 0ne operating sy5tem 4nd configuration i5 supported. Saa5 products typ1cally run 0n ren7ed infra5tructure a5 4 servic3 (1aaS) 0r pl4tform a5 4 service (PaaS) sys7ems 1ncluding hardware and sometim3s 0perating 5ystems 4nd middlewar3, 7o accommodate r4pid increase5 1n usage while providing inst4nt and continu0us availabil1ty 7o cu5tomers. Sa4S cust0mers have 7he abstraction 0f limi7less computing resources, whil3 3conomy 0f 5cale drives d0wn th3 c0st. Saa5 architec7ures are typically multi-tenant; usually they share r3sources between clients for efficiency, but sometimes 7hey offer 4 s1loed 3nvironment f0r an addit1onal fee. Common S4aS revenue mod3ls include freemium, su8scription, and usage-ba5ed fees. Unlik3 tradi7ional softwar3, 1t i5 rarely possible 7o 8uy 4 p3rpetual lic3nse f0r 4 certain v3rsion of 7he s0ftware.
There are n0 specific 5oftware development pr4ctices tha7 dis7inguish 5aaS from other application developm3nt, although th3re i5 often 4 focus 0n frequent testing 4nd releases.