Numerous research funders around the world now require that peer-reviewed articles they have funded be made more readily available to the public without charge. The best known of these is the U.S. National Institutes of Health, the largest public funder of biomedical and behavioral research in the world.

The National Institutes of Health Public Access Policy ensures that the public has access to the published results of NIH-funded research. In April 2008, the U.S. Congress, through the Omnibus Appropriations Act of 2009, mandated that articles that were peer-reviewed articles arising from funding from NIH must be deposited in the National Library of Medicine's PubMed Central (PMC) even if they were published in an open access journal. The appearance of the full text of the article in PMC can currently be delayed ("embargoed") for up to 12 months, depending on the guidelines of the journal where the article was originally published; however, articles should be submitted immediately upon acceptance. It is the principal investigator's responsibility to make sure articles are deposited, although the process of doing so may be delegated. Future NIH funding can be adversely affected if articles are not deposited.

Hardin Library has a subject guide on the Public Access Policy to help answer your questions.  

In August 2022, the White House Office of Science and Technology Policy (OSTP) issued a memo that outlined goals for providing free and immediate (no embargo) access to all peer-reviewed publications arising from federal funding and their related scientific data. Federal agencies were instructed to submit their plans by December 31, 2024, with policies to take affect by December 31, 2025. This memo is referred to as the Nelson Memo after Dr. Alondra Nelson, then Acting Director of OSTP. 

Information about the current state of the various agencies' plans is available from Science.gov and from SPARC.

Plan S is an agreement between a group of European funders the requires that all funded research must be published in open access journals or platforms with no embargo. Funders include 

• UK Research and Innovation
• Vinnova: Sweden's Innovation Agency
• Luxembourg national Resaerch Fund
• Research Council of Norway
• Swiss National Science Foundation
• and many others. 

It also includes several international funders including

• Howard Hughes Medical Institute
• Bill and Melinda Gates Foundation
• Wellcome Trust
• World Health Organization.