neo4j-nvl-skill

---name: neo4j-nvl-skilldescription: Neo4j Visualization Library (NVL) — framework-agnostic graph rendering for the browser.compatibility: @neo4j-nvl/base 1.1+; React 19 for @neo4j-nvl/react; modern browsers with Canvas2D + WebGL2version: 1.0.1allowed-tools: Bash WebFetch---

When to Use

• Rendering a Neo4j graph in a browser (vanilla JS, React, Vite) with custom interactions, rendering, or data shapes
• Visualizing driver.executeQuery results as an interactive graph
• Wiring zoom, pan, drag, click, hover, lasso, or box-select interactions
• Embedding NVL inside an existing app and synchronizing graph state

When NOT to Use

• Pre-styled embedded graph view with default behavior, no custom interactions → GraphVisualization from @neo4j-ndl/react (Neo4j Needle / NDL design system) — wraps NVL with default Neo4j styling. See Use NVL or the Needle Component? below.
• Python / Jupyter notebook graph visualization → neo4j/python-graph-visualization (the Python port of NVL)
• Writing/optimizing Cypher → neo4j-cypher-skill
• Driver setup / executeQuery / sessions → neo4j-driver-javascript-skill
• Server-side data fetching with no rendering → neo4j-driver-javascript-skill
• GDS algorithm execution → neo4j-gds-skill or neo4j-aura-graph-analytics-skill
• GraphQL API → neo4j-graphql-skill

---

Use NVL or the Needle Component?

Need	Use
Embed a graph view with default Neo4j styling, no custom interactions or rendering	GraphVisualization from @neo4j-ndl/react (Neo4j Needle / NDL design system) — wraps NVL and accepts records shaped { id, labels, properties: { key: { stringified, type } } } (NeoNode)
Custom interactions, custom rendering, non-standard data shapes, or framework-agnostic embedding	This skill — use NVL directly

If the answer is the first row, install and use the Needle component instead of NVL — do not duplicate styling work.

---

Install

npm install @neo4j-nvl/base                  # core (required)
npm install @neo4j-nvl/interaction-handlers  # standard interactions (optional, vanilla JS)
npm install @neo4j-nvl/react                 # React wrappers (optional)

Peer requirements: React 19 for @neo4j-nvl/react. The published peerDependency range still permits React 18, but mixing major versions is not recommended — target 19. @neo4j-nvl/layout-workers is a transitive dependency — never install directly. neo4j-driver is a peer of @neo4j-nvl/base only when using nvlResultTransformer.

Starter templates: https://github.com/neo4j-devtools/nvl-boilerplates — official per-framework scaffolds; prefer these over hand-rolled setups.

License: NVL ships under the Neo4j Visualization Library License — for use with Neo4j products only. Cannot be used against other graph backends.

---

Pick the Right Paradigm

Need	Use
React app, default interactions	<InteractiveNvlWrapper> from @neo4j-nvl/react
React app, custom interaction wiring	<BasicNvlWrapper> + own handlers via ref
Vanilla JS, standard interactions	NVL + @neo4j-nvl/interaction-handlers
Vanilla JS, fully custom event logic	NVL + container.addEventListener + nvl.getHits()
Static PNG/SVG image export	<StaticPictureWrapper> or nvl.saveToFile() / nvl.saveToSvg()

---

Pick the Right Renderer

Renderer	Max nodes	Detail	Use case
'canvas' (default)	~1,000	Full captions, icons, arrows, pixel-perfect hit-testing	Detail investigation, small graphs
'webgl'	100,000+	Reduced label fidelity (bound by GPU max texture size)	Large-scale pattern exploration

const nvl = new NVL(container, nodes, rels, { renderer: 'webgl' })
nvl.setRenderer('canvas')   // swap at runtime

---

Container Setup

The container must have an explicit width AND height. Missing height → container collapses to 0 → graph invisible. Most-reported NVL bug.

<!-- ❌ height defaults to 0; graph invisible -->
<div id="viz"></div>

<!-- ✅ explicit dimensions -->
<div id="viz" style="width: 100%; height: 600px;"></div>

---

Vanilla — Base Library

import { NVL } from '@neo4j-nvl/base'

const container = document.getElementById('viz')
const nodes = [{ id: '1' }, { id: '2' }]
const relationships = [{ id: '12', from: '1', to: '2', type: 'KNOWS' }]

const nvl = new NVL(container, nodes, relationships)

With options + callbacks:

import { NVL } from '@neo4j-nvl/base'

const options = {
  initialZoom: 1.0,
  minZoom: 0.1,
  maxZoom: 8,
  layout: 'forceDirected',
  renderer: 'canvas',
  styling: { defaultNodeColor: '#0e86d4', defaultRelationshipColor: '#888' }
}
const callbacks = {
  onInitialization: () => console.log('NVL ready'),
  onLayoutDone: () => nvl.fit([]),
  onError: (err) => console.error('NVL error', err)
}

const nvl = new NVL(container, nodes, relationships, options, callbacks)

// On teardown — always:
nvl.destroy()

NVL constructor signature: new NVL(frame, nvlNodes?, nvlRels?, options?, callbacks?). All but frame are optional and default to empty.

---

Vanilla — Interaction Handlers

Compose handlers onto an existing NVL instance. Each handler registers callbacks via .updateCallback(name, fn) and must be torn down with .destroy().

import { NVL } from '@neo4j-nvl/base'
import {
  ZoomInteraction, PanInteraction, DragNodeInteraction,
  ClickInteraction, HoverInteraction, BoxSelectInteraction,
  LassoInteraction, KeyboardInteraction
} from '@neo4j-nvl/interaction-handlers'

const nvl = new NVL(container, nodes, relationships)

const zoom  = new ZoomInteraction(nvl)
const pan   = new PanInteraction(nvl)
const drag  = new DragNodeInteraction(nvl)
const click = new ClickInteraction(nvl, { selectOnClick: true })
const hover = new HoverInteraction(nvl, { drawShadowOnHover: true })

click.updateCallback('onNodeClick',         (node, hits, evt) => console.log('node',  node.id))
click.updateCallback('onRelationshipClick', (rel,  hits, evt) => console.log('rel',   rel.id))
click.updateCallback('onCanvasClick',       (evt)             => console.log('canvas'))
hover.updateCallback('onHover',             (el, hits, evt)   => el && console.log('over', el.id))
drag.updateCallback('onDragEnd',            (nodes, evt)      => savePositions(nodes))
zoom.updateCallback('onZoom',               (level)           => console.log('zoom', level))

// Teardown — destroy all handlers, then the NVL instance
function teardown() {
  for (const h of [zoom, pan, drag, click, hover]) h.destroy()
  nvl.destroy()
}

Disable an event without removing the handler: click.removeCallback('onCanvasClick'). Passing true instead of a function enables the event with a no-op (useful for default selection behavior).

---

React — InteractiveNvlWrapper

Pre-wires every interaction handler. Toggle events with mouseEventCallbacks (function = on + callback; true = on, no-op; false/omit = off).

import { InteractiveNvlWrapper } from '@neo4j-nvl/react'
import type { MouseEventCallbacks, NvlOptions } from '@neo4j-nvl/react'
import { useRef } from 'react'
import type { NVL } from '@neo4j-nvl/base'

export function GraphView({ nodes, rels }) {
  const nvlRef = useRef<NVL>(null)

  const nvlOptions: NvlOptions = { initialZoom: 1, renderer: 'canvas' }

  const mouseEventCallbacks: MouseEventCallbacks = {
    onNodeClick:         (node, hits, evt) => console.log('node',  node.id),
    onRelationshipClick: (rel,  hits, evt) => console.log('rel',   rel.id),
    onCanvasClick:       (evt)             => console.log('canvas'),
    onHover:             (el, hits, evt)   => el && console.log('hover', el.id),
    onDragEnd:           (nodes, evt)      => persist(nodes),
    onZoom: true,                                       // enable, no callback
    onPan:  true
  }

  return (
    <div style={{ width: '100%', height: 600 }}>
      <InteractiveNvlWrapper
        ref={nvlRef}
        nodes={nodes}
        rels={rels}
        nvlOptions={nvlOptions}
        interactionOptions={{ selectOnClick: true, drawShadowOnHover: true }}
        mouseEventCallbacks={mouseEventCallbacks}
        onInitializationError={(err) => console.error('NVL init', err)}
      />
    </div>
  )
}

ref resolves to the underlying NVL instance — call any method on it: nvlRef.current?.fit([]), nvlRef.current?.setRenderer('webgl'), nvlRef.current?.saveToFile().

---

React — BasicNvlWrapper + Ref

No interactions wired. The ref exposes every NVL method via IncludeMethods<NVL> — use when building custom interaction logic in React.

import { BasicNvlWrapper } from '@neo4j-nvl/react'
import type { NVL } from '@neo4j-nvl/base'
import { useRef } from 'react'

export function MiniGraph({ nodes, rels }) {
  const nvlRef = useRef<NVL>(null)

  return (
    <div style={{ width: '100%', height: 400 }}>
      <BasicNvlWrapper
        ref={nvlRef}
        nodes={nodes}
        rels={rels}
        nvlOptions={{ initialZoom: 2 }}
        nvlCallbacks={{ onLayoutDone: () => nvlRef.current?.fit([]) }}
      />
      <button onClick={() => nvlRef.current?.fit(['1', '2'])}>Zoom to 1,2</button>
    </div>
  )
}

---

Wiring a Neo4j Driver Result

@neo4j-nvl/base exports a ResultTransformer for the JS driver that deduplicates nodes/relationships across any record shape.

import neo4j from 'neo4j-driver'
import { NVL, nvlResultTransformer } from '@neo4j-nvl/base'

const driver = neo4j.driver(process.env.NEO4J_URI,
  neo4j.auth.basic(process.env.NEO4J_USERNAME, process.env.NEO4J_PASSWORD))

const { nodes, relationships } = await driver.executeQuery(
  'MATCH (a)-[r]-(b) RETURN a, r, b LIMIT 25',
  {},
  { database: 'neo4j', resultTransformer: nvlResultTransformer }
)

const nvl = new NVL(document.getElementById('viz'), nodes, relationships)

// ❌ raw EagerResult — records are not Node/Relationship objects
const result = await driver.executeQuery('MATCH (a)-[r]-(b) RETURN a, r, b')
new NVL(container, result.records, [])   // breaks

// ✅ use the transformer
const { nodes, relationships } = await driver.executeQuery(
  'MATCH (a)-[r]-(b) RETURN a, r, b',
  {},
  { database: 'neo4j', resultTransformer: nvlResultTransformer }
)
new NVL(container, nodes, relationships)

For driver lifecycle, session management, Integer handling, and TypeScript types → neo4j-driver-javascript-skill.

---

Updating the Graph

Method	Behavior
addAndUpdateElementsInGraph(nodes, rels)	Insert new; update existing by id (only specified fields)
updateElementsInGraph(nodes, rels)	Update existing only; ignores unknown ids
addElementsToGraph(nodes, rels)	Insert only; throws on existing id
removeNodesWithIds(ids)	Remove nodes; adjacent relationships auto-removed
removeRelationshipsWithIds(ids)	Remove relationships
setNodePositions(nodes, updateLayout?)	Override positions; optionally re-run layout
restart(options?, retainPositions?)	Restart with new options; positions optional

Diff updates use PartialNode / PartialRelationship — only id is required:

nvl.updateElementsInGraph(
  [{ id: '1', color: '#f00', selected: true }],   // PartialNode
  [{ id: '12', width: 4 }]                         // PartialRelationship
)

---

Hit Testing (Manual)

Use when NOT using the interaction-handlers package. getHits() resolves which node/relationship is under a pointer event.

const nvl = new NVL(container, nodes, rels)

container.addEventListener('click', (evt) => {
  const { nvlTargets } = nvl.getHits(evt, ['node', 'relationship'], { hitNodeMarginWidth: 4 })
  const hitNode = nvlTargets.nodes[0]
  const hitRel  = nvlTargets.relationships[0]
  if (hitNode) console.log('hit node', hitNode.data.id)
  else if (hitRel) console.log('hit rel', hitRel.data.id)
  else console.log('hit canvas')
})

HitTargetNode / HitTargetRelationship carry data, pointerCoordinates, distance, insideNode (nodes only). See references/api-surface.md.

---

Common Mistakes

Mistake	Fix
Container with no height → invisible graph	Set explicit width and height on the container
Pass driver.executeQuery result directly	Use nvlResultTransformer and consume { nodes, relationships }
WebGL for small label-rich graphs	Use 'canvas'; labels are fully supported
Canvas for 10k+ nodes	Switch to 'webgl' via renderer option or setRenderer
New NVL per React render	Use <InteractiveNvlWrapper> / <BasicNvlWrapper> or wrap in useEffect + destroy()
Forgetting nvl.destroy() on teardown	Call destroy() on unmount; React wrappers handle this automatically
Vanilla handlers not torn down	Call .destroy() on every interaction before nvl.destroy()
Worker construction blocked (strict CSP / sandboxed runtime / older bundler)	nvlOptions: { disableWebWorkers: true } (NVL has a non-worker fallback)
Telemetry enabled in regulated env	nvlOptions: { disableTelemetry: true }
Layout never settles	Pin anchor nodes with pinNode(id); tune layoutTimeLimit
selectOnClick fires double	Toggle once at mount; don't flip interactionOptions per render
Hit test misses near node edge	Pass { hitNodeMarginWidth: N } to getHits
Captions missing on WebGL	GPU max texture size exceeded; fall back to Canvas or shrink captions

---

References

Load on demand:

• references/api-surface.md — complete NVL method table; Node, Relationship, NvlOptions, LayoutOptions, ExternalCallbacks, HitTargets, NvlMouseEvent, StyledCaption, Point; every interaction-handler class + its options + its callback signatures; React <InteractiveNvlWrapper> / <BasicNvlWrapper> / <StaticPictureWrapper> props; MouseEventCallbacks and KeyboardEventCallbacks shapes; named exports inventory; nvlResultTransformer signature
• references/troubleshooting.md — zero-height container, build-tool-agnostic disableWebWorkers fallback, Canvas/WebGL trade-offs + WebGL2 note, WebGL texture-size cap, onWebGLContextLost recovery, telemetry opt-out, memory leaks, stuck layouts, double selection, hit-margin tuning, license restriction

Canonical web documentation (use WebFetch when references above are insufficient):

• https://neo4j.com/docs/nvl/current/ — user guide (installation, base library, interaction handlers, React wrappers)
• https://neo4j.com/docs/api/nvl/current/ — TypeDoc API reference
• https://neo4j.com/docs/api/nvl/current/examples.html — runnable examples
• https://github.com/neo4j-devtools/nvl-boilerplates — official starter templates per supported framework
• https://github.com/neo4j/python-graph-visualization — Python port of NVL (use this skill only for the JavaScript/browser path)

---

Checklist

• Container has explicit width AND height CSS
• Correct paradigm chosen from the decision table (vanilla / handlers / React)
• Renderer matches expected node count (Canvas ≲1k / WebGL 100k+)
• Driver executeQuery results piped through nvlResultTransformer
• database specified on every executeQuery call (delegate to neo4j-driver-javascript-skill)
• All interaction handlers .destroy()-ed before nvl.destroy() on teardown
• nvl.destroy() called on React unmount (manual instances only — wrappers handle it)
• disableTelemetry: true set when in regulated / offline environments
• disableWebWorkers: true set when bundler / CSP blocks worker construction
• Graph updates use addAndUpdateElementsInGraph / updateElementsInGraph — not restart
• License compatible: target is a Neo4j product