Despite the increasing ubiquity of computer-based tests, many general qualifications examinations remain in a paper-based mode. Insufficient and unequal digital provision across schools is often identified as a major barrier to a full adoption of computer-based exams for general qualifications. One way to overcome this barrier is a gradual adoption, involving a dual running of paper-based and computer-based exams. When an exam is offered in both modes, and results from both are treated as equivalent, the comparability between modes needs to be ascertained. This includes examining whether the mode in which students respond to extended writing questions such as essays, either by handwriting or by typing on the computer, introduces systematic differences. This article presents findings from a review of existing literature on writing mode effects. Specifically, it discusses findings on four comparability aspects: scores, marking, text characteristics and composing processes. It also offers recommendations for practice.