In some examples, a method includes selecting, by a coding computing device, a particular identifier from a set of identifiers generated by an identifier allocation authority, wherein the set of identifiers are included within a global set of identifiers maintained by the identifier allocation authority; coding, by the coding computing device, the particular identifier from the set of identifiers into an optical element set that represents an optical code comprising a plurality of finder optical elements arranged in a pattern to localize the optical code within an image, a plurality of context optical elements representing context information, and a plurality of content optical elements representing content information; and generating a visual output of the optical code that is decodable to the particular identifier which, in combination with at least one other parameter associated with the optical element set, comprises a globally unique identifier in a set of globally unique identifiers.