HAtom

hAtom is a microformat designed to mark up blog posts in HTML so that software can extract structured data from ordinary web pages. It provides a lightweight, machine-readable representation of a post’s essential metadata within standard HTML markup.

In practice, hAtom relies on class-based annotations to identify the parts of a post, including the title, content, author, published date, and a permalink. A post is typically wrapped in a container marked to indicate a post entry and contains sub-elements for the title and content, while the author may be represented through a nested structure such as a person or organization.

The primary goal of hAtom is to expose metadata in a machine-readable form without requiring a separate feed or a different document structure. Applications such as feed readers, search engines, and data aggregators can discover new posts by detecting hAtom markup on a page and then follow the link to the original article.

History and usage context place hAtom in the early microformats movement. It originated with Microformats 1 in the mid-2000s as part of an effort to annotate human-readable HTML with structured data. Over time, the emergence of Microformats 2 and schema.org-based markup reduced its prevalence, though some sites still employ hAtom or have migrated to newer microformat patterns.

As part of the microformats family, hAtom shares goals with other formats like hCard and hCalendar: enabling better interoperability between human-readable pages and machine processing by embedding semantic data directly in HTML.