External Metadata

External metadata in the context of web accessibility refers to supplementary information stored separately from a web page that can be applied to improve the page's accessibility without modifying the original source code. This approach allows volunteers, developers, or automated systems to create accessibility fixes — such as alternative text for images, heading structures, or reading order corrections — that are layered onto existing web content through browser extensions or proxy services. External metadata is particularly valuable when site owners are unwilling or unable to fix accessibility issues directly, enabling third-party remediation at scale. The concept was pioneered by projects like the W3C ALT-server (1997) and IBM's Social Accessibility project, which used standardized metadata specifications to allow collaborative accessibility improvements.