When looking for video to include in a multimedia project, it is important to be aware of how resolution and compression can impact the aesthetic of your piece. Resolution is the number of pixels running horizontally and vertically in your image.
The standard resolution for a project that combines video, image and audio elements is HD (1920x1080). If you don't want your video to have artifacts, make sure the files you download are at least 1920 pixels x 1080 pixels. You can check your files resolution by opening in a media player or video application and checking the properties of the video.
Some websites that allow download of videos also give the option for different formats. Since these files are usually heavily compressed, downloading the larger file type typically (not always) means it will be less compressed.
Prelinger Archives– collection of home movies, amateur films, and important films made by or produced for US corporations, nonprofit organizations, community interest groups, educational institutions and more.
Pixabay– Stock videos available for download at high resolution
National Park Service– B-roll available for download of National Parks
National Marine Sanctuaries Media Library - Select video clips and high-resolution still images from America's underwater treasures.
Yellowstone National Park Video Library - llibrary of public domain video available for download from Yellowstone National Park
The Open Video Project– a shared digitial video collection
Library of Congress– material in the Library’s National Screening room collection available for download
open-video.org - Deveoped by UNC-Chapel Hill, Open-Video is a repository of digitized video content intended for multimedia retrieval, digital library, and other research communities.
C-SPAN content is easy to search from their video search site. There is a simple one-box search and an advanced search screen that allows for limiting by date, as well as by thematic category, topic, and series.