# Platform overrides To specify platform-specific information in rockspecs, one should use the `platforms` field of top-level tables. In top-level tables, a field `platforms` is treated specially. If present, it may contain a table containing sub-tables representing different platforms. For example, `build.platforms.unix`, if present, as the name implies, would be a table containing specifics for building on Unix systems. The contents of platform tables override the contents of the top-level table where `platforms` is located. For example, in a Linux system, an entry `build.platforms.linux.foo` will override `build.foo`. Tables are scanned deeply, so if `build.foo` is a table, the contents of `build.platforms.linux.foo` will add to or replace the contents of `build.foo`, instead of just replacing the entire table. Therefore, you don't need to rewrite the entire `build` section in a platform table, only the fields should change.