nonindexed

Nonindexed refers to items that are not included in a given index. An index is a data structure or system that supports efficient lookup by associating keys or terms with their locations. When something is nonindexed, it is not searchable through that index, or it has been deliberately excluded from indexing.

In web publishing and search engine optimization, a page can be nonindexed by design. Operators use noindex directives, such as a meta robots noindex tag or an HTTP header like X-Robots-Tag: noindex, to signal search engines not to include the page in their indexes. Additionally, restricting access with robots.txt can prevent crawlers from discovering content, though robots.txt alone does not guarantee nonindexing because some engines may index a URL without content if it is linked from other pages. Nonindexed pages may still be accessible to users if linked internally or externally, but they will not appear in search results.

In databases and information systems, nonindexed data refers to data not covered by an index. Absence of an index on a column means that queries filtering on that column typically require full scans, reducing performance for large datasets. Indexing trade-offs include faster queries and increased write and storage costs; thus, some data remains nonindexed by design.

The concept also applies to document repositories and content management systems, where certain items are kept out of search or catalog indices for privacy, compliance, or workflow reasons.

See also: indexed, noindex, robots.txt, robots meta tag, search engine indexing.