Registration rights are contractual rights letting preferred stockholders require the company to register their shares with the SEC for public sale. They come in three flavors: demand registration (the holder forces a filing), piggyback registration (the holder rides on a company-initiated filing), and S-3 registration (short-form post-IPO filing), with the practical effect of letting investors actually sell shares in the public markets after an IPO. It is a critical structural right because preferred stockholders cannot freely sell their shares post-IPO without their shares being registered or qualifying for an exemption like Rule 144.
The three main types of registration rights: