Graphviz Online

Graphviz Online is a browser-based editor and renderer for the Graphviz DOT language, created by the developer "dreampuf" and hosted as a static site at dreampuf.github.io/GraphvizOnline. It is a thin, client-side front end over the classic Graphviz toolkit: rather than calling a server, it bundles viz.js, a build of Graphviz's C code compiled to JavaScript via Emscripten, so all layout and rendering happen locally in the browser. The editing surface is the ACE code editor, and the resulting diagram is displayed as SVG with interactive pan and zoom (via svg-pan-zoom and Hammer.js for touch). The project is small and permissively licensed (BSD-3-Clause).

Its data model is exactly Graphviz's own: users type or paste graph/digraph definitions in the DOT language, and the tool re-runs layout on each edit to produce a live preview. Because it wraps the real Graphviz engine, it exposes the standard layout algorithms, dot for hierarchical/layered graphs plus neato, fdp, sfdp, twopi, circo, osage, and patchwork for force-directed, radial, and treemap-style arrangements, and can emit the usual output targets including SVG, PNG, and the Graphviz Plain textual layout. It is essentially the same rendering path you would get from the Graphviz command line or a library such as NetworkX' DOT export, but with zero installation.

In the graph-data and format-conversion landscape it occupies the "visualize a DOT file quickly" niche. It reads only DOT; it does not import GraphML, GEXF, or other exchange formats, so it is typically the last step after a converter (for example generating DOT from another model with GraphInOut or Graph::Easy) rather than a hub itself. Convenience features aimed at sharing include a ?url= parameter to load a graph from a Gist or any public URL, and a ?presentation= parameter (with flags such as editable, hide-options, show-download) to embed a clean, editor-free rendered view.

Strengths are its simplicity, offline-capable client-side rendering, faithful use of upstream Graphviz layout, and easy URL-based sharing and embedding. Limitations follow from being a wrapper: it accepts only DOT input, provides no graph-editing GUI (unlike Graphviz, which targets the same engine with a visual layer), performance and memory are bounded by the WebAssembly/JS build for very large graphs, and it depends on the bundled viz.js version for which Graphviz features and attributes are available.