The word "data" is traditionally considered a plural noun, derived from Latin, and it is often used with a plural verb (e.g., "the data are"). However, in everyday usage, especially in the fields of computing and information technology, "data" is frequently treated as a mass (or uncountable) noun, taking a singular verb (e.g., "the data is").
In academic and formal contexts, it's best to use "data" as a plural noun, but in more casual settings, it's acceptable to treat it as uncountable. In summary, it can be considered both countable (in the plural sense) and uncountable depending on the context.