I am a big fan of study preregistration which includes also pre-registration of systematic reviews. PROSPERO is a perfect place for that as it

accepts registrations for systematic reviews, rapid reviews and umbrella reviews. PROSPERO does not accept scoping reviews or literature scans. Sibling PROSPERO sites registers systematic reviews of human studies and systematic reviews of animal studies.

So I wrote a protocol (basically the method section of the review), downloaded a few papers, constructed a score sheet and entered a few papers to see if my data collection scheme is complete and if my R program is running correctly.

But when I tried to enter the study into the preregistration form, it was no more possible if you read  the following notice carefully

Before completing a registration form, please check that your review is eligible for inclusion in PROSPERO

• Registration should take place once the systematic review protocol has been finalised, but ideally before screening studies for inclusion begins. However, reviews are currently accepted for registration as long as they have not started data extraction.
• Completed reviews should not be registered.
• PROSPERO only accepts registration of systematic reviews with a health related outcome.
• Cochrane reviews should not be registered individually (we are working towards uploading these electronically)

as it prohibits any data extraction.

So I believe, that most entries in PROSPERO are by authors with supranormal power who know how their data will look like in advance. Or are they simply ignoring the fact that data extraction may not have been started?

I any case, the database is slow and many records outdated while it seems that it is still stuck with COVID19 …