Providing free access to relevant resources is crucial for prisoners' personal development, well-being and, ultimately, rehabilitation. By offering a variety of reading and learning materials, from easy to expert levels and in various languages, prison libraries provide lifelong learning opportunities, thereby improving inmates' chances of successful reintegration on release. Reductions in recidivism have substantial societal and cost-saving benefits. The policy brief "How prison libraries support rehabilitation efforts" highlights that prison libraries should not operate in isolation, but work closely with the local (public) library system. They need to be managed by qualified prison library staff with access to sufficient budget and resources. Implementing and funding a well-functioning prison library service is a cost-effective way of sharing valuable resources by creating a constructive and transformative meeting and learning space with far-reaching and lasting effects. Taking security issues into account, inmates should be able to enjoy the same-quality library services and materials available to citizens living in freedom. This policy brief is based on the findings of the UIL publication "Books beyond bars: The transformative potential of prison libraries." It has been further refined through consultation with the global "IFLA Working Group on Prison Libraries."