Whenever I play Factorio I have never seen an edge to the map. I assume it must be procedural. Is there a maximum size to how far the map will extend, either in any one direction or in total area?
According to the Factorio Wiki (https://wiki.factorio.com/World_generator#Maximum_Map_Size_and_used_Memory):
The map size is limited to 2,000 x 2,000 kilometers; internally, this is a square 2,000,000 tiles on a side, with an area of 4,000,000,000,000 (4 trillion) square tiles (assuming 1 tile = 1 meter on a side yields 2,000 x 2,000 km = 4 million square km). In real-world terms, this is between the sizes of India and Australia (or about 40% the area of the United States, or over 10 times the area of Germany). It would take around 240 game-minutes (=4 hours real time) by train to reach that border from the center. This makes the world essentially endless for practical purposes.
Because chunks are only generated in and close around the area revealed by radar, it is possible to reach that border without overloading your computer, as the size of the map in computer memory is dependent only on chunks actually generated. If only a narrow stripe of land is explored to far away, this remains manageable.
The generated chunks are fully mapped and stored in the player's RAM, which is the practical limiting factor of exploration.
So unlike what Gedas says, it's not ACTUALLY infinite size, but rather limited to a square with edges of 2,000 km.