Codex4 is a web directory maintained as a field notebook of the open internet. Each entry in the catalogue represents a site that has been observed, noted, and filed under the appropriate subject section. The record currently holds 831 entries distributed across 22 fields, from chance-games operators to dental clinics, from legal practices to travel outfitters.

The directory operates on a simple principle: every listed site appears as an equal specimen. There are no rankings, scores, or editorial tiers. A site either meets the basic criteria for listing or it does not. Accepted entries are placed in the section that best describes their subject matter and remain in the catalogue until the domain ceases to resolve.

Subject sections vary considerably in size. The chance-games field is the most densely catalogued, with 117 entries. The uncatalogued and general-listings section holds 189 specimens that resist easy classification. The property and land section is the smallest, with five entries. These differences reflect observed specimen density, not editorial preference.

Codex4 accepts new submissions at no cost. Site operators can use the submission form to propose an entry. Submissions are reviewed against basic criteria before being added to the field record. Review is periodic; not all submissions will be accepted, and the directory does not correspond with submitters individually.

The catalogue is updated as new entries are approved and as dormant entries are retired. Codex4 does not publish a schedule for updates. The current record represents the state of the catalogue as of the most recent review cycle.