File Format

Blender features an internal file system that can pack multiple scenes into a single file (called a ".blend" file).

• All of Blender's ".blend" files are forward, backward, and cross-platform compatible with other versions of Blender, with the following exceptions:
  • Loading animations stored in post-2.5 files in Blender pre-2.5. This is due to the reworked animation subsystem introduced in Blender 2.5 being inherently incompatible with older versions.
  • Loading meshes stored in post 2.63. This is due to the introduction of BMesh, a more versatile mesh format.
• All scenes, objects, materials, textures, sounds, images, post-production effects for an entire animation can be stored in a single ".blend" file. Data loaded from external sources, such as images and sounds, can also be stored externally and referenced through either an absolute or relative pathname. Likewise, ".blend" files themselves can also be used as libraries of Blender assets.
• Interface configurations are retained in the ".blend" files.

A wide variety of import/export scripts that extend Blender capabilities (accessing the object data via an internal API) make it possible to inter-operate with other 3D tools.
Blender organizes data as various kinds of "data blocks", such as Objects, Meshes, Lamps, Scenes, Materials, Images and so on. An object in Blender consists of multiple data blocks – for example, what the user would describe as a polygon mesh consists of at least an Object and a Mesh data block, and usually also a Material and many more, linked together. This allows various data blocks to refer to each other. There may be, for example, multiple Objects that refer to the same Mesh, and making subsequent editing of the shared mesh result in shape changes in all Objects using this Mesh. Objects, meshes, materials, textures etc. can also be linked to from other .blend files, which is what allows the use of .blend files as reusable resource libraries.