A demanding part of doing a systematic review, that also requires collaboration, is screening and selection of studies. Using a tool for this can greatly faciltate the process. You can read more about screening here.

Rayyan

Rayyan is a free to use web tool, that also has mobile applications for Android and iOS. There are no limits in the number of reviews that can be created by a user.

You can import references to Rayyan in a number of formats (EndNote export .enw, RIS, CSV, PubMed XML and Web of Science/CIW). However, we strongly recommend that you collect all your references from different searches in a reference manager, remove duplicates and export the references as a RIS-file, that is then imported to Rayyan. If needed, you can add new batches of references at any time during the screening process. Different filters help you get an overview of the material, such as keywords, topics, geographic origin, language, publication types and year.

There are a number of different functions in Rayyan that makes screening easier:

Collaborative screening where you can choose to turn blinding on or off and have access to a review chat
Possibility to include reason to why a reference should be excluded
Labelling of keywords for inclusion and exclusion (highlighted with green and red)
Rayyan learns from your inclusions/exclusions and rates references on how probable they are for inclusion

Full text PDF can be uploaded to each individual article.

Abstrackr

Abstrackr is a free to use web tool, that are simple to use and get started with. The interface is a little sparse and it is still in beta, but it has several functions that make collaboration for selecting studies easier:

Pilot round for training where everyone screen the same abstracts in order detect possible conflicts and refine inclusion-/exclusion criteria
Rate studies for either inclusion, exclusion or maybe
Tag studies with terms that are either linked to inclusion or exclusion
Possibility to add notes to individual studies
Track progress and conflicts

As the screening process Abstrackr will provide predictions for the relevance of remaining studies and abstracts can be sorted by their relevance in the screening interface.

However, uploading references for a new project can be a little cumbersome and there is no support for uploading fulltext for the next step of screening.