Downloading copyrighted online content legally requires the permission of the copyright holder, according to the Copyright Clearance Center. Digital and electronic content receives the same copyright protection as copyrighted material in more traditional formats.
Most material found online is subject to copyright law, even if it does not contain a copyright notice. This includes websites, music recordings, email and works embedded in websites, explains the Copyright Clearance Center.
Some material on the Internet may be legally downloadable under the doctrine of fair use, which allows use of copyrighted material for the purposes of scholarship and commentary. However, as the Stanford Copyright and Fair Use Center points out, it is generally best to ask the author of any material for permission before downloading or otherwise copying it.