HathiTrust is a public access digital library that preserves more than 18 million digitized items in their Digital Library, including several collections of government documents. All of their materials can be read for free under the fullest extent allowable by U.S. and international copyright law.
One of HathiTrust's many collections is a collection of U.S. Federal Documents, as identified via the HathiTrust Federal Government Documents Registry. It is a work in progress, and is updated regularly to add and remove content.
Another collection that you can find on HathiTrust is their collection of the U.S. Congressional Serial Set volumes. This collection is updated as items are added to the HathiTrust repository.
If you have any questions or need any search tips, please check out How to Search and Access.
The Federal Register is the official daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents. It is updated daily by 6 a.m. and is published Monday-Friday, except for Federal holidays.
You can find the Federal Register on GovInfo, dating all the way back to volume 1. Copies of volumes 60 to present are available for download as an entire issue or as smaller sections. Volumes 59 and older are digitized versions of historical issues that are made available as full issue PDF only.
You can also use FederalRegister.gov, which was created as a way to make it easier for citizens and communities to understand the regulatory process and to participate in Government decision-making. You can use the search bar to search for a term or citation. Please note that documents that are older than 1994 are only searchable using their Federal Register citation.
If you have any questions, please check out their handy Reader Aids section, where they have helpful guides like Using FederalRegister.Gov.
The Code of Federal Regulations is the codification of the general and permanent rules published in the Federal Register by the departments and agencies of the Federal Government.
The CFR on GovInfo is current with the published print version of the CFR. When the print editions are released, the online version is also made available. GovInfo has titles ranging from 1996 to the present. These are added concurrent with the release of the paper editions. When revised CFR volumes are added, the prior editions remain on GovInfo as a historical set.
You can also find the Code of Federal Regulations on eCFR.gov. By using eCFR, you can: browse the Code of Federal Regulations as it existed at any point in time; compare the regulations as they existed on any two dates; view a timeline of how the CFR content has changed; search for specific terms; and subscribe to changes in the regulations. Please note that this is not an official legal edition of the CFR, it is simply an excellent resource that makes searching the CFR easier that is continuously updated and provides enhanced feature that are not part of the published CFR.
Like FederalRegister.gov, you can use some handy Reader Guides to learn more about how to navigate eCFR. There's Navigating to Content of Interest, Reading eCFR Content, and eCFR Changes Through Time.