This chapter focuses on the technical aspects of emoji, including how emoji are encoded and rendered for use in digital communication. The chapter explains how emoji are developed by the Unicode Consortium as well as considering the social implications of this process. Unicode characters, and emoji codepoints, modifiers, and sequences are explained. The chapter also deals with emoji design and aesthetics, and explains how emoji are visually rendered as glyphs by different ‘vendors’ such as social media platforms. The chapter then examines the role of semiotic technologies in both enabling and constraining the ways they are used. It concludes by discussing the implications of emoji encoding and rendering on corpus construction, annotation, and concordancing.