This chapter provides the first comprehensive overview of hardware integrated circuits (IC) protection by metering. Hardware metering, or IC metering refers to mechanisms, methods, and protocols that enable tracking of the ICs post-fabrication. Metering is particularly needed in the horizontal semiconductor business model where the design houses outsource their fabrication to (mostly offshore) contract foundries to mitigate the manufacturing and labor costs. The designers and/or the design intellectual property (IP) holders are vulnerable to piracy and overbuilding attacks due to the transparency of their designed IP to the foundry that requires a complete description of the design components and layout to fabricate the chips. Because of the prevalence of counterfeit and overbuilt items, and the widespread usage of ICs in a variety of important applications, the problem has recently gained an increased attention by the industry, government, and research community. Post-silicon identification and tagging of the individual ICs fabricated by the same mask is a precursor for metering: In passive metering, each ICs is specifically identified, either in terms of its functionality, or by other forms of unique identification. The identified ICs may be matched against their record in a pre-formed database that could reveal unregistered ICs or overbuilt ICs (in case of collisions). In active metering, not only the ICs are uniquely identified, but also parts of the chip’s functionality can be only accessed, locked (disabled), or unclocked (enabled) by the designer and/or IP rights owners with a high level knowledge of the design that is not transferred to the foundry. We provide a systematic view of the field, along with the first detailed taxonomy and descriptions of the various passive and active hardware metering methods available.