Academic publishers fall broadly into two categories: subscription and open access, which take different approaches to copyright.
However, open preprint servers since the 1990s increased the scale and visibility of this process and raised the question as to whether this constituted 'prior publication' or merely 'sharing'.
The majority of academic journal publishers now accept submission of articles that have already been shared as preprints, with copyright of this version remaining with the author by default.
For journals following a subscription model, where articles are accessed via a paywall, copyright is transferred from author to publisher.
The rise of "gold" open access academic journals stands in contrast to this, where copyright is retained by the author and a reuse license (typically a creative commons variant) applied.