iTXt

iTXt is a PNG ancillary chunk used to store international textual data within a PNG image. It stores UTF-8 text and supports optional compression and language tagging, enabling multilingual metadata alongside the image data.

The iTXt chunk data includes a keyword, a null separator, a compression flag, a compression method, a language tag (RFC 3066), a translated keyword (UTF-8), and the text content. If the compression flag is set to 1, the text is compressed with the zlib/deflate method; otherwise the text is stored uncompressed as UTF-8.

Compared with tEXt and zTXt, iTXt provides UTF-8 support and explicit language tagging, in addition to optional compression. tEXt stores text in ISO-8859-1 without compression, while zTXt stores compressed text using the zlib format. iTXt unifies these capabilities by offering multilingual, UTF-8 text with optional compression.

Usage of iTXt includes metadata such as titles, descriptions, or author credits in multiple languages within the image file. The language tag helps clients display the appropriate translation, and the translated keyword clarifies the meaning of the text for different locales.

iTXt is an optional, ancillary PNG chunk. Decoders that do not support iTXt will typically ignore it, so metadata stored in iTXt should not be relied upon for essential rendering or processing. As with other PNG metadata, it should be treated as supplementary information.