IRIs

An Internationalized Resource Identifier (IRI) is a generalization of the Uniform Resource Identifier (URI) that allows Unicode characters to appear in resource identifiers. IRIs enable identification of resources using non-Latin scripts and characters while preserving the structure of URLs used on the Internet.

Any URI is an IRI, but not every IRI is a URI. Implementations that require ASCII can convert an IRI to a URI by encoding all non-ASCII characters in UTF-8 and percent-encoding the resulting octets. Conversely, a URI may be represented as an IRI by interpreting its ASCII characters as Unicode where appropriate.

IRIs are defined by RFC 3987 and designed to be backward-compatible with existing URI-based protocols. In practice, domain labels may be converted to ASCII via IDNA (punycode) for transmission in environments that require ASCII; non-ASCII portions of the path, query, and fragment may be percent-encoded.

Examples include http://例子.测试/路径?参数=值, which corresponds to a URI with a punycode host and percent-encoded path and query. Tools and libraries provide IRI support; when possible, be explicit about encoding to ensure interoperability across browsers, servers, and APIs.

Security and interoperability considerations include the need for normalization, handling homographs, and consistent comparison. IRIs are widely supported in modern web standards and XML/HTML processing, but legacy systems may require conversion to ASCII URIs.