For more information for preprint authors, see Recommendations for Authors and the accompanying blog post.
Many, but not all, publishers allow preprint posting of manuscripts then later submitted to their journals for publication. Some publishers such as BMJ and Springer Nature encourage preprint archiving. Use the resources listed below for a quick check for specific journal/publisher policies on preprints, and it is wise to also check the current policy in the author instructions for any journal you are preparing to submit to.
Many funders and employers are recognizing the value of preprints and allowing them to be included in metrics for assessment.