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A content review can be limited to one or more reviewers that must undertake the approval. These reviewers are added by the workflow on the transition into the content review state.
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There is no option to manually assign any other reviewers
all the reviewers must undertake and agree on the approval decision (either approve or reject) for a transition to occur
assigned reviewers can only be changed by editing the added workflow
The workflow assignment of a reviewer can be
an individual user
a list of multiple users
users who are members of one or more Confluence user groups
Note that a user can also be pre-assigned by the workflow to an assignable content review but the pre-assigned reviewers can be unassigned using the workflow popup.
Minimum Reviewers
An approval can be set to require a minimum number of reviewers to undertake an approval decision and agree to either approve or reject the content for the transition to occur.
The required minimum number of reviewers will be displayed as an outline avatars in the workflow popup but only if the required minimum is greater than the number of pre-assigned mandatory reviewers.
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individual reviewer approved decisions are displayed in the workflow popup until the minimum number of reviewers have undertaken the review
if more reviewers are assigned than the required minimum the transition will occur when the minimum number of reviewers agree even if there are reviewers who have not yet undertaken the review
the transition will not occur if at least one current decision by a reviewer disagrees with the approval decision