OpenRaster

OpenRaster is an open standard file format for layered raster graphics. It is intended to be an open, vendor-neutral alternative to proprietary formats such as PSD, enabling interoperable editing across different graphics software. The format is maintained by the OpenRaster project, hosted at openraster.org.

An OpenRaster document is stored as a ZIP archive with the .ora extension. The archive typically contains a MIME type file declaring image/openraster, a directory with per-layer image data (usually PNGs) and a structured XML manifest that describes the layer tree, properties (such as opacity and visibility), and the relationships between layers, including groups and masks. This structure allows software to preserve the multi-layer composition and non-destructive editing when exchanging files.

Interoperability is a core goal: applications that support OpenRaster can export and re-import layered work without forcing a flattening step, supporting round-trip editing and more flexible workflows across editors.

History and status: The format emerged from open-source graphics communities, with Krita and others driving its development in the 2010s. It has since gained broader acceptance in the free-software ecosystem, and is supported by several compatible editors, with ongoing development maintained by the OpenRaster project.