This report describes and discusses developments in the violent extremist and terrorist online scene(s) in the 12-month period from 1 January 2023 to 31 December 2023. It accomplishes this by surveying, synopsising, and integrating the findings of relevant articles and reports produced by academics, think-tanks, civil society, and governmental organisations; high quality press reports; and the first-hand online experience and primary research of the authors. The report is divided into four major parts: Part I focuses on the online aftermath of Hamas’ massive marauding terrorist attack in southern Israel on 7 October 2023; Part II on online Jihadism, particularly that linked to al-Qaeda and the so-called ‘Islamic State’ (hereafter IS); Part III focuses on the online activities of the extreme right, particularly its European and US variants; and Part IV details the responses of a range of legislators and Internet companies to online extremist and terrorist activity over the course of the last 12 months. We conclude by pointing to a five issues in the violent extremism and terrorism online realm(s) that bear watching in 2024.