Methods and arrangements for identifying content, and employing such identification, are detailed. One method embeds a plural-bit digital watermark into content, but first checks to see if the content is previously watermarked. Another method applies a digital watermark detection procedure to only a sub-portion of a digital content item. Yet another arrangement involves plural-portion content, where one portion is watermarked with first data governing its rights management, and another portion is watermarked with second data governing its rights management. Still another method concerns distribution of content items, where each is watermarked with a unique ID as part of the distribution process. Yet another method concerns deriving an identifier from content, and using the content to access related metadata from a remote computer system. A variety of other technologies and improvements are also detailed.