When you submit a research manuscript for peer review, the journal may report the status of the review as “in review” or “under review”.
From a purely grammatical perspective there’s not much difference between the two terms. It may be that one journal uses the term “in review” and another the term “under review”, both to signify the same thing: that your academic paper is now being reviewed by experts in your field.
Some journals may however use both terms to represent different stages of the review process. In this case you’ll see the status of your submitted paper change from “in review” to “under review”:
This means that you have successfully submitted your manuscript to the journal and your submitted documents are now being verified. This part of the submission process will include ensuring that you have uploaded all necessary documents and that the content of your manuscript is suitable for the theme of the journal. This initial review process is typically performed by one of the editorial staff at the journal.
When the status of your manuscript changes to under review, this means that it has passed the initial editorial checks. The journal has confirmed that you’ve uploaded and submitted the correct documents and that the content of your paper is relevant to your journal. The status of under review means that the paper has been sent to external expert reviewers and your paper is now being assessed by them.
Note however that some journals may use the reverse of the above if making a distinction between the two terms. That is to say that some journals may have the status of the submitted paper as under review whilst they assess its suitability for review and the status in review when it’s actually being assessed by reviewers.
You may also notice that the date associated with the status of under review changes even though the actual status does not. In these cases, it’s likely an update from the journal to indicate that the associate editor has sent the manuscript to a new peer reviewer for assessment.
This sometimes happens during the peer review process where the journal editor may send out the submitted manuscript to several potential reviewers who don’t respond with a decision or recommendation; to progress the review process, the editor then sends the manuscript to different reviewers. This is one of the reasons why the peer review timeline can sometimes be so variable.
It’s becoming more common for journals or the corresponding author to make a preprint version of your journal submission available to read. After you receive reviewer comments and have submitted a revised manuscript, then this revision may then also be made available in an early sharing format. Following the final decision, the accepted manuscript should be the publication version that replaces the previous versions of the submission that were made available as preprints.
You should have the option to not make your project work publicly available under it’s been peer reviewed; in some cases this may be a requirement placed on you by your funders.