Normally, as per ICAO standards, localizers are commissioned to 25 nm in the course sector and 17 nm out to 35 degrees off centerline.
In the U.S., and possibly other places, frequency congestion has brought about reduced coverage localizers which are 18 nm in the course sector and 10 nm out to 35 degrees off centerline.
There are also long-range facilities in the U.S., with coverage far exceeding the normal specifications.
Cheers,
/Fred