“You have downloaded your article from the website of the journal and you think that, since it is available free, you can deposit this published version in HAL. Well, sometimes it is true but …. sometimes it is not.
Does the mention “Open Access” or “Open” is included in your file? or a Creative Common license (CC-BY, CC-BY-NC, etc) ? If so, you can deposit this publisher’s version in HAL. You sometimes need good eyes to find the licence: in the Elsevier’s files, it is at the bottom of the first page (example); idem for the articles published by Oxford University Press (example). On the other hand, for articles in journals published by Nature Publishing Group and MDPI, the licence is on the last page of the file (example).
But if these mentions are not included in the file, you cannot deposit the published version without first checking if the publisher approves it….”