  We introduce CityJSON Text Sequences (CityJSONSeq in short), a format based
on JSON Text Sequences and CityJSON. CityJSONSeq was added to the CityJSON
version 2.0 standard to allow us to stream very large 3D city models. The main
idea is to decompose a CityJSON dataset into its individual city objects (each
building, each tree, etc.) and create several independent JSON objects of a
newly defined type: 'CityJSONFeature'. We elaborate on the engineering
decisions that were taken to develop CityJSONSeq, we present the open-source
software we have developed to convert to and from CityJSONSeq, and we discuss
different aspects of the new format, eg filesize, usability, memory footprint,
etc. For several use-cases, we consider CityJSONSeq to be a better format than
CityJSON because: (1) once serialised it is about 10% more compact; (2) it
takes an order of magnitude less time to process; and (3) it uses significantly
less memory.
