A systematic review protocol:
The protocol should be developed before you actually begin your systematic review. This will ensure your review is carefully planned. By developing a protocol, the purpose, rationale, hypothesis, and methods you plan to use in your review are well considered and explicitly documented.
Here are some guidelines on protocol reporting. They can help you understand the key elements in a protocol and plan your protocol.
Once you have written your protocol, it is advisable to register it. This will help avoid other people conducting a review similar to your topic and reduce unnecessary duplication of research effort.
Note that: Some journal publishers, such as BMJ Open and Systematic Reviews, require protocol registration prior to starting the systematic review. The protocols will be published as with research articles.
PROSERO - aims to provide a comprehensive list of completed and in-progress systematic reviews. Read this page for details on completing the protocol registration form. Note: PROSPERO does not accept scoping review protocols.
Further reading: Pieper, D., & Rombey, T. (2022). Where to prospectively register a systematic review. Systematic Reviews, 11(1), 8-8.