viszed

Viszed is an open-source framework for building interactive data visualizations in the web browser. It offers a declarative, data-first approach that lets developers describe visual encodings, layouts, and data transformations in a single specification. It can target rendering outputs such as SVG, Canvas, and WebGL, from simple charts to complex dashboards.

Created by the Viszed Collective, a network of developers and data journalists, public releases began in the early 2020s with a stable version in 2023. The project emphasizes modularity, extensibility, and interoperability with common web tooling and is distributed under a permissive open-source license.

The specification defines data sources, scales, marks, layouts, and interactions in a JSON- or YAML-like format. Viszed supports reactive data flows so updates propagate through transforms into encodings. Features include data transformations, a library of marks, theming, accessibility options, and plugin hooks for custom marks and adapters to connect with external data sources and other visualization tools.

Usage appears among data journalists, educators, and startups seeking rapid prototyping. Critics point to a smaller ecosystem and potential performance challenges for large datasets. Nevertheless, Viszed is noted as a concise example of a declarative framework that links data processing directly to visual representation on the web.