Free and Open Source Software (FOSS) constitutes the bulk of the SoftwareCommons, and is at the heart of our digital society. We discuss why and howthe Software Heritage project is taking over the mission of ensuring that thisprecious body of knowledge will be preserved over time and made available toall. The Software Commons is the vast body of human knowledge embedded in softwaresource code, that is publicly available and can be freely altered and reused.Free and Open Source Software (FOSS) constitutes the bulk of it. Sadly we seemto be at increasing risk of losing this precious heritage built by the FOSScommunity over the paste decades: code hosting sites shut down when theirpopularity decreases, tapes of ancient versions of our toolchain (bit-)rot inbasements, etc. The ambitious goal of the [SoftwareHeritage](https://www.softwareheritage.org) project is to contribute toaddress this risk, by collecting, preserving, and sharing _all_ publiclyavailable software in source code form. Together with its complete VCSdevelopment history. Forever, of course. By doing so Software Heritage will serve the needs of: Society, by preservingour collective technological heritage; Industry, by building the largestsoftware provenance open database; Science, by assembling the largest curatedarchive for software research; and Education, by creating the ultimateanthology for programming curricula. Although still in Beta, Software Heritage has already archived more than 3billion unique source code files and 700 million unique commits, spanning morethan 45 million FOSS projects from major software development hubs, GNU/Linuxdistributions, and upstream software collections. Software Heritage is developed transparently as a collaborative project andall its own source code is available as FOSS under copyleft licenses.Currently incubated by [Inria](http://www.inria.fr/en), the project willgraduate soon to an independent charitable, nonprofit organization.