See this previous discussion: https://www.researchgate.net/post/Is_MDPI_a_predatory_journal_publisher_from_China

The crucial question is how one defines "predatory publisher". I think the definition "a predatory journal/publisher is one that is included in Beall's list" is not sufficient. We would have to apply Beall's criteria (or any other criteria following from the definition we apply) to journals' and publishers' current actions (Beall's list is a bit older, after all).

To me, a predatory journal would be one that 'ambushes' prospective authors by letting them go through the review process and hitting them with a fee after their article is accepted, i.e. by hiding the publication fees until the author is committed. I don't think this applies to MDPI journals (but I don't really know).

However, there is a much larger class of publisher-driven journals which are controlled by the publishers, limit the authority of the scientific community, and manipulate peer review in order to guarantee speedy publication and low rejection rates. This is not predatory in the sense I described above. However, the business practice of selling publication opportunities to desperate authors (which, unfortunately, has become possible with the 'author pays' open adccess model) undermines the quality control of scientific communities. In the long run, this might be more dangerous to scientific communities than predatory journals.

Frankly, five years ago I wouldn't remotely have considered publishing anything with MDPI, but they have improved substantially over the last years and now my most recent publication is with them. I will continue spreading over different publishers for future works, but I may submit something there again at some point.

They are still a quite pushy with the goal of rapid publishing, but at no point did I experience the reviewing process as unserious or predatory. Of course I can't say anything about those old reports about stuff being published despite reviewers comments being ignored since I didn't do that.

I published with mdpi everything seemed professional from reviewers to production. I got a large discount on one paper and 100% discount on my last submission. So i dont think its all about the money. They seem to be trying to improve their reputation. all open access journals do charge. It is time consuming to run a journal. I have seen what i thought was a horrible allowed publication by nature communications supper high impact factor where the reviews where down on a paper but was accepted anyway see Ouyang et al. “Albedo changes caused by future urbanization contribute to global warming” . The journal is biased on this subject in my opinion so there are issues with all journals.

I published with mdpi everything seemed professional from reviewers to production. I got a large discount on one paper and 100% discount on my last submission. So i dont think its all about the money. They seem to be trying to improve their reputation. all open access journals do charge. It is time consuming to run a journal. I have seen what i thought was a horrible allowed publication by nature communications supper high impact factor where the reviews where down on a paper but was accepted anyway see Ouyang et al. “Albedo changes caused by future urbanization contribute to global warming” . The journal is biased on this subject in my opinion so there are issues with all journals.

I published with mdpi everything seemed professional from reviewers to production. I got a large discount on one paper and 100% discount on my last submission. So i dont think its all about the money. They seem to be trying to improve their reputation. all open access journals do charge. It is time consuming to run a journal. I have seen what i thought was a horrible allowed publication by nature communications supper high impact factor where the reviews where down on a paper but was accepted anyway see Ouyang et al. “Albedo changes caused by future urbanization contribute to global warming” . The journal is biased on this subject in my opinion so there are issues with all journals.

I published with mdpi everything seemed professional from reviewers to production. I got a large discount on one paper and 100% discount on my last submission. So i dont think its all about the money. They seem to be trying to improve their reputation. all open access journals do charge. It is time consuming to run a journal. I have seen what i thought was a horrible allowed publication by nature communications supper high impact factor where the reviews where down on a paper but was accepted anyway see Ouyang et al. “Albedo changes caused by future urbanization contribute to global warming” . The journal is biased on this subject in my opinion so there are issues with all journals.

I published with mdpi everything seemed professional from reviewers to production. I got a large discount on one paper and 100% discount on my last submission. So i dont think its all about the money. They seem to be trying to improve their reputation. all open access journals do charge. It is time consuming to run a journal. I have seen what i thought was a horrible allowed publication by nature communications supper high impact factor where the reviews where down on a paper but was accepted anyway see Ouyang et al. “Albedo changes caused by future urbanization contribute to global warming” . The journal is biased on this subject in my opinion so there are issues with all journals.

I published with mdpi everything seemed professional from reviewers to production. I got a large discount on one paper and 100% discount on my last submission. So i dont think its all about the money. They seem to be trying to improve their reputation. all open access journals do charge. It is time consuming to run a journal. I have seen what i thought was a horrible allowed publication by nature communications supper high impact factor where the reviews where down on a paper but was accepted anyway see Ouyang et al. “Albedo changes caused by future urbanization contribute to global warming” . The journal is biased on this subject in my opinion so there are issues with all journals.