Blueprints are build plans that allow players to save their facilities for future use and rebuild them in an instant later on. They are shared across save files, allowing the player to expedite construction in any playthrough once they have a blueprint saved.
Unlocking
Blueprints are unusable until the Mass Construction upgrade is researched. Initially, only small facilities (up to 150 buildings) can be saved as a blueprint. However, upgrading Mass Construction will increase the limit until eventually any number of buildings can be saved.
Notably, the Mass Construction upgrade also restricts what blueprints can be used, not just those that can be created. For example, if a player has saved a blueprint with 1000 buildings in it, then starts a new save file, they will not be able to construct that blueprint until they research Mass Construction up to the appropriate level.
Mechanics
Selecting Blueprint in the hotbar will bring up the Blueprint Library, which shows all saved blueprints and also allows the player to make new ones. From here, selecting Create New Blueprint (or pressing CTRL + C) will put the player into blueprint mode, where they can draw a selection box to select all the facilities they would like to be in the blueprint. Right-clicking on a facility that has been selected will deselect it.
Each blueprint has a title, thumbnail title, icon(s), and description.
Additionally, the proportions of the planetary grid where the blueprint is created versus where it is placed cannot be significantly different. For instance, creating a blueprint at a planet's pole then attempting to build it at the planet's equator will not work. Additionally, tropic lines interfere with blueprint construction in several ways: if the blueprint is on top of a tropic line when it is created, then it must be placed on the same tropic line; otherwise, if the blueprint was not on top of a tropic line when created, then it cannot be placed on a tropic line at all.
Swarm Blueprint
Swarm Blueprints are unusable until the Solar Sail Orbit System is researched. These are accessed through the Dyson Sphere editor, rather than the normal blueprint screen, and do not require researching Mass Construction. Swarm blueprints can only be copies or pasted, using the "Swarm Blueprint" copy and paste buttons in the Dyson Swarm editor's left hand column Dyson Swarm area. These swarm blueprints and contains information on all swarm orbits in the currently selected solar system. There is no in-game way to save these blueprints, however they use the Operating System's clipboard for their copy/paste and are encoded in printable characters -- so it is possible to save then by switching to a text editor program, pasting the blueprint text, and saving that file. Such a saved blueprint could be imported into a new game of DSP by opening the saved text file, selecting the contents and then copying them into the system clipboard, at which point the Swarm Blueprint 'Paste' button will be active in the game and you can paste the saved blueprint.
Shell Blueprints
Shell Blueprints are unusable until the Vertical Launching Silo is researched. These are accessed through the Dyson Sphere editor, rather than the normal blueprint screen, and do not require researching Mass Construction. Shell blueprints can only be copies or pasted, using either the "Selected Layer(s)" or "All Layers" copy and paste buttons in the Dyson Swarm editor's left hand column Dyson Sphere area. Despite the name "Selected Layer(s)" will only be available when exactly one (1) layer is selected and its copy button will copy design of that selected layer but not its radius, inclination, or longitude of (AN). To paste a shell blueprint of a layer you first must create the target layer, which will define its radius, inclination, and longitude of (AN) and then you can use the "Selected Layer(s)" paste button paste the design onto the selected layer. (You can paste the same design onto multiple layers, but you'll need to select and paste them one by one) If zero, or multiple layers are selected then only "All Layers" will be shown. The "All Layers" copy button will copy the entire Dyson Sphere, including each layer's radius, inclination, or longitude of (AN). You can paste an all layers shell blueprint onto a blank shell with any number of existing layers, from 0 - 10. Any existing layers that also exist in the blueprint will replace the layers defined in the target; however shell blueprints cannot be pasted over a layer or sphere with any defined structure (even unbuilt structure) as you will have to delete the structure (or the entire layer) before pasting the blueprint. Also DSP will adjust each layer's radius as necessary to avoid conflicting with an existing defined layer or due to different orbital size ranges between the source and target star. Shell blueprints also use the system clipboard and can be saved and used in new games using a text editor, just as with swarm blueprints.
Sphere Blueprints
Sphere Blueprints are unusable until the Solar Sail Orbit System is researched. These are accessed through the Dyson Sphere editor, rather than the normal blueprint screen, and do not require researching Mass Construction. Sphere blueprints can only be copies or pasted, using the "Sphere Blueprint" copy and paste buttons in the Dyson Swarm editor's right hand column Dyson Sphere area. Sphere blueprints copy both swarm blueprints and all layer blueprints as a single blueprint.