YGF

YGF, the "Y Graph Format," is the native binary graph format developed by yWorks for its yFiles diagramming libraries and the freely available yEd graph editor. Unlike text-based interchange formats, a YGF file is an opaque binary object stream: it is produced and consumed by the yFiles class YGFIOHandler, which serializes and deserializes the graph structure together with its visual representation directly through the library's object model. As a result the format is tightly coupled to yFiles internals and cannot practically be read or written outside the yWorks toolchain.

The format is designed to capture the full range of graph structures that yFiles supports. It stores the vertices and edges of the graph, their on-canvas layout (node positions, edge paths and bend points), and the "realizers" that describe how each element is drawn (shapes, colors, labels and similar visual properties). Notably, YGF also preserves hierarchical, grouped graphs — folder and group nodes with nested contents — retaining all relevant nesting information, which simpler flat formats such as TGF or basic GML cannot express.

Within yEd, YGF is classified as an "alternative" graph format rather than the recommended one. yWorks steers users toward GraphML 1.1 (and its compressed .graphmlz variant) as the standard native format, because GraphML is an open, XML-based, extensible representation that stores structure, graphics and arbitrary custom properties losslessly and can be inspected or transformed with ordinary XML tooling. The yEd documentation warns that when saving to alternative formats like YGF "some information may not be stored and retrieved again," and yFiles more broadly deprecated its Java-serialization-based I/O in favor of GraphML realizer serializers.

In the graph-data and format-conversion landscape YGF is therefore a legacy, single-vendor artifact of limited interoperability: its main practical use is exchanging complete yEd/yFiles diagrams — including grouping and full styling — between yWorks applications. For any workflow that needs portability, diffability, or third-party parsing, GraphML is the preferred substitute, and tools such as yEd itself or GraphInOut are typically used to move data into more open formats. Reliable, well-documented conversion from YGF outside yEd is scarce precisely because of its closed binary encoding.