Anything you create that is fixed in a tangible form (such as a written document) has automatic copyright protections. Registering your copyright with the U.S. Copyright Office allows you better legal standing to seek statutory damages and lawyer fees in a copyright infringement lawsuit.
When you work with a publisher, you sign an author's agreement that gives some or all of your copyrights away. You need to know the terms of your author's agreement in order to know how you can use or post your own work.
Publisher policies and agreements vary considerably, and there may be restrictions in how you may distribute your own work. Publisher’s policies typically appear on their website, on your contract, or in Sherpa/Romeo, a database of publisher policies.
Publisher policies are generally organized around the different versions of the work, including:
There may be conditions that you must follow in sharing your work, such as linking to the published version.
Some publishers offer their own sharing platforms that offer read-only access to non-subscribers. These platforms also captures article usage statistics so that authors can demonstrate the impact of their work.