This website appeared as an attempt to collect the dwindling and non-superficial information about the diverse world of feature phone operating systems, thriving in 00s and decaying since then.
Feature phones are surrounded with numerous myths. Just a few of them:
Feature phones run some common "Java" operating system, boosted by profane articles and phone catalogs; it comes from a smartphone-centric thinking implying that an operating system equals an application platform. In reality, Java was almost never used outside of third-party apps and SIM cards. "Almost" means there were exceptions, like Jasper S20 running SavaJe OS, or BlackBerry smartphones having a proprietary superset of Java ME, which many of stock applications are using too, or the Motorola Timeport P1088 prototype running Elate OS with all stock apps made in Java.Feature phones don't run any other operating systems, but rather some "firmware".It was true for some very early cellphones, as all firmware was one monolith application there talking with hardware directly. But the complexity quickly arose to a level when separating an operating system kernel from applications became crucial, even though they could remain a common project. "Firmware", also known as "ROM", is a term unrelated to "OS"; even high-end smartphones have their operating system packed into a big firmware image and flashed all in a whole. This is a general approach for any mobile and embedded devices, opposed to PCs where an operating systems is installed file-by-file, and you can use the same image to install an operating systems to many different computers, while phone ROMs are necessarily baked for one certain device.Anything with a phone keyboard is a dumb phone capable only of calls/SMS and a few other basic features.I see this myth not only from youngsters, but also from older people who have barely ever seen smartphones with a hardware keyboards, or even powerful feature phones, as they were too expensive for them and their surrondings in 00s.
In general, feature phones run not even one, but at least two operating systems. They have two processors called AP (Application Processor) and BP (Baseband Processor). BP is tiny and weak, and lives in the cellular module providing the connectivity; it lives on its own and may directly interact with speakers and microphones, but the user generally doesn't interact with it directly. AP, on the other hand, is relatively powerful and runs the interface a user is interacting with, and all the luxury features besides of basic calling phones got stuffed with. Smartphones have the same separation. This website lists operating systems for APs if other is not specified explicitly; baseband operating systems are a vast world worthy of special consideration.
Most feature phones have a Harward architecture, which means the operating system with all native apps are baked into one big image and not in separate files, meaning you cannot easily modify it, upgrade individual apps, install or remove them. Historically, it was the main thing which distinguished feature phones from smart phones, but some feature phones, especially modern ones (if you still call them so) running KaiOS, have applications as separate files too internally.
Use links in the top bar to navigate to articles about specific operating systems and devices.