Q: Whom will the journal editor contact, the first author or the corresponding author?

As a practice, the journal editor contacts only the corresponding author. It is simpler and more efficient for the editor to have only one point of contact (correspondence) for the manuscript even if there are multiple authors for the paper. So too there should be only one author – the corresponding author – contacting the editor. The editor may have a query for some other author in the manuscript, but it has to be routed through the corresponding author. Similarly, the corresponding author has to collate all the queries and comments from the other authors and send them together to the editor. Nowadays, a few journals do allow more than one corresponding author, but this has to be established before making the submission, through a presubmission query.

Related reading:

• Can I write to the editor if I'm the first author but not the corresponding author?
• What corresponding authors are expected to do after journal submission
• Does your target journal allow more than one corresponding author? A case study