A systematic review protocol describes the rationale, hypothesis, and planned methods of the review. It should be prepared before a review is started and used as a guide to carry out the review.
Detailed protocols should be developed a priori, made publicly available, and registered in a registry such as those listed below.
There are many reporting standards available which outline the essential information you need to provide in a protocol. Requirements will change depending on where you will publish the protocol. Some of these standards include:
PRISMA-P (Preferred Reporting Items for Systematic review and Meta-Analysis Protocols) 2020 checklist: recommended items to address in a systematic review protocol:
PROSPERO - a public register which registers protocols and specifies essential registration fields which must be completed to describe the planned review in appropriate detail.
Joanna Briggs Institute - JBI registers protocols and specifies the components that comprise a JBI protocol in its reviewer's manual.
Cochrane Handbook, Chapter 4 provides a Guide to the Contents of a Cochrane Protocol and Review.
For interventions, or accuracy of diagnostic tests:
For social interventions in education, crime and justice, social welfare:
For reviews in health or social care:
Cochrane Handbook for Systematic Reviews of Interventions by 
The following documents from the CONSORT (Consolidated Standards of Reporting Trials) website.
MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines.
PRISMA stands for Preferred Reporting Items of Systematic Reviews and Meta-Analyses.
The EQUATOR Network is an “umbrella” organisation that brings together researchers, medical journal editors, peer reviewers, developers of reporting guidelines, research funding bodies and other collaborators with mutual interest in improving the quality of research publications and of research itself.