Anything public can be used to invalidate a patent. The first to file only refers to two inventors patenting the same non public (or public in the span of a ye

Anything public can be used to invalidate a patent. The first to file only refers to two inventors patenting the same non public (or public in the span of a year) invention. Anything public for more than a year cannot be patented because there's prior art (obviously). So if you want to ensure someone don't sue you for a patent, you just have to publish everything you've been using. Of course this is a lie, because there's always a patent that you can be sued, because even if you can invalidate said patent (even with another patent), you will still have to pay a lot of money.