TanStack Query isFetching vs isLoading vs isPending - Each Flag Tracks a Different Phase

isFetching, since it is true only during the initial mount and false during every subsequent background refetch.

isPending, since it is scoped specifically to the first fetch and remains false for all later refetches regardless of cache state.

isLoading, since it represents the first fetch specifically, whereas isFetching is true any time a request is in flight (including background refetches) and isPending is true whenever no data exists yet, including on every remount with an empty cache.

All three flags are functionally identical aliases maintained for backward compatibility, so any of them can be used interchangeably for this purpose.