Learn Finnish: Kaikki, mikä ilmestyy syötteeseen, yksilöityy. - Everything that appears in the feed becomes individualized.

It is derived from the noun yksilö (an individual). By adding the automative suffix -öityä, it becomes a verb describing a spontaneous process or transformation. Here, it means "to become individualized" or "to become personalized" on its own, without a direct external agent.

If yksilöityä means "to become individualized", how would I say "to individualize" as an active action?

To express the active version of doing this to an object, you would use the suffix -öidä, giving you the verb yksilöidä (to individualize or to specify). The -öityä suffix in our sentence strictly describes the process happening to the subject itself.

Why does the sentence use mikä as the relative pronoun instead of joka?

While joka is the standard relative pronoun for referring back to a specific noun, mikä is used when referring back to pronouns that represent an aggregate, an absolute, or an abstract whole. Because the antecedent here is kaikki (everything), it must be followed by mikä.

What is the base form of syötteeseen, and why is it in this case?