Introduction - Hollebrands, Anderson and Oliver Section 1: Design of Online Learning Experiences in Mathematics Education (4) Chapter 1: Marcelo C. Borba, Johann Engelbrecht and Salvador Llinares. Using digital technology and blending to change the mathematics classroom. Chapter 2: Angie Hodge-Zickerman, Patrick R. Lowenthal, and Cindy S. York. Teaching mathematics education online: Instructional design theories, strategies, and technologies Chapter 3: Naomi Jessup, Jennifer Wolfe, and Crystal Kalinec-Craig. Rehumanizing mathematics education and building community in online spaces Chapter 4: Dung Tran and Giang-Nguyen T. Nguyen. Keep human interaction present in online mathematics education methods courses - lenses of educators across institutions Section 2: Formal Online Learning Experiences for Prospective Teachers (7) Chapter 5: Jeannette D. Alarcón, Carrie S. Cutler, Jennifer B. Chauvot, and Susie L. Gronseth. Applying critical pedagogy and UDL to synchronous online course design to equip pre-service teachers in mathematical discourse Chapter 6: Yves Kreis, Ben Haas, Zsolt Lavicza, and Robert Weinhandl Transition from traditional over hybrid towards online courses for pre-service elementary school teachers at the University of Luxembourg Chapter 7: Hollylynne Lee, Rick Hudson, Stephanie Casey, Gemma Mojica, William Finzer, Heather Barker, and Taylor Harrison. Preparing teachers to teach statistics through online curriculum modules: Design, implementation, and results Chapter 8: Ceneida Fernández, Salvador Llinares, and Yoilyn Rojas. The impact of an online teacher education program on the development of prospective secondary mathematics teachers' noticing Chapter 9: Ji-Yeong I, Christa Jackson, and Ricardo Martinez. Online learning to teach mathematics for emergent bilinguals Chapter 10: Suparna Chatterjee, Germain Degardin, Wanda Bulger-Tamez, Erika Acosta, Rachel Boren. Restructuring content assessment in mathematics teacher education courses using digital interactive notebooks Chapter 11: Simon Byeonguk Han and Eva Thanheiser. Number Talks in asynchronous online classrooms for more equitable participation and formative assessment of student thinking. Section 3: Formal Online Learning Experiences for Practicing Teachers (5) Chapter 12: Nathan A. Hawk, Margaret A. Bowman, and Kui Xie. Theory-based intervention framework to improve mathematics teachers' motivation to engage in online professional development Chapter 13: Jeffrey Choppin, Julie Amador, Cindy Callard, Cyndi Carson, Ryan Gillespie, Jen Kruger, and Stephanie Martin A Three-Part Synchronous Online Model for Middle Grades Mathematics Teachers' Professional Chapter 14: Armando Paulino Preciado Babb and Ayman Aljarrah. Contemporary, emergent mathematics for teachers: A case study on an online graduate program Chapter 15: Aimee J. Ellington, Jamey Lovin, Kristina Anthony, Heather Nunnally, Erica R. Miller & V. Rani Satyam Preparing K-8 mathematics specialists in an (a)synchronous flipped online program Chapter 16: Verónica Vargas-Alejo and Luis E. Montero-Moguel. Didactic sequence implemented in an online modeling course for inservice teachers. Section 4: Informal and Self-Directed Learning (4) Chapter 1