In an era of heightened accountability and expanding educational technology choices, mathematics educators must critically assess the effectiveness of the tools available to them. While deciding on technological tools, it is essential that we not only promote rigor in mathematics but also ensure closing learning gaps and improve students' beliefs about their own abilities to learn. The aim of this study was to evaluate two personalized learning platforms, IXL and Khan Academy, to determine their mathematical rigor and the extent to which their designs promote mastery learning (Bloom, 1968) and the growth mindset (Dweck, 2006). This descriptive qualitative study first assessed mathematical rigor using a revised Bloom's taxonomy (Boeren & Iniguez-Berrozpe, 2022). Secondly, the promotion of mastery learning and growth mindset was evaluated through a detailed case-study narrative analysis, utilizing rubrics developed specifically for this study. Data was obtained through interactions with each platform, both as a teacher and a student, and from teacher reviews on Common Sense Education. The findings suggest that both IXL and Khan Academy offer comparable mathematical rigor for 7th-grade proportional relationships skills. Additionally, both platforms' designs seem similarly effective in promoting mastery learning. However, Khan Academy's design appears to more effectively foster a growth mindset, particularly in how it addresses incorrect student responses. The implications of this study are that personalized learning platforms can be critically evaluated so educators can make informed decisions about which best support the enhancement of student learning and beliefs, and ease teacher workloads so they can better serve students. Additionally, insights from this study can guide the development and improvement of these platforms. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]