ComfyUI Frontend Extensions

Custom nodes can extend the ComfyUI frontend with JavaScript. Extensions register hooks, widgets, commands, settings, and UI components.

Quick Start

1. Export WEB_DIRECTORY in Python

# __init__.py
WEB_DIRECTORY = "./js"
__all__ = ["WEB_DIRECTORY"]

2. Create JavaScript Extension

// js/my_extension.js
import { app } from "../../scripts/app.js";

app.registerExtension({
    name: "my_nodes.my_extension",

    async setup() {
        console.log("Extension loaded!");
    },
});

All .js files in WEB_DIRECTORY are loaded automatically when ComfyUI starts.

Extension Hooks (Lifecycle Order)

init — After canvas created, before nodes

app.registerExtension({
    name: "my.ext",
    async init(app) {
        // Modify core behavior, add global listeners
    },
});

addCustomNodeDefs — Modify node definitions

async addCustomNodeDefs(defs, app) {
    // defs is a dict of all node definitions
    // Can add or modify definitions before registration
    defs["MyFrontendNode"] = {
        input: { required: { text: ["STRING", {}] } },
        output: ["STRING"],
        output_name: ["text"],
        name: "MyFrontendNode",
        display_name: "My Frontend Node",
        category: "custom",
    };
},

getCustomWidgets — Register custom widget types

getCustomWidgets(app) {
    return {
        MY_WIDGET(node, inputName, inputData, app) {
            const widget = node.addWidget("text", inputName, "", () => {});
            widget.serializeValue = () => widget.value;
            return { widget };
        },
    };
},

beforeRegisterNodeDef — Modify node prototype

async beforeRegisterNodeDef(nodeType, nodeData, app) {
    if (nodeData.name === "MyNode") {
        // Chain onto prototype methods
        const origOnCreated = nodeType.prototype.onNodeCreated;
        nodeType.prototype.onNodeCreated = function () {
            origOnCreated?.apply(this, arguments);
            // Add custom widget, modify behavior, etc.
            this.addWidget("button", "Run", null, () => {
                console.log("Button clicked!");
            });
        };
    }
},

nodeCreated — After node instance created

nodeCreated(node, app) {
    if (node.comfyClass === "MyNode") {
        // Modify this specific node instance
        node.color = "#335";
    }
},

setup — After app fully loaded

async setup(app) {
    // Add event listeners, register UI components
    app.api.addEventListener("executed", (event) => {
        console.log("Node executed:", event.detail);
    });
},

loadedGraphNode — When loading saved graph

loadedGraphNode(node, app) {
    if (node.comfyClass === "MyNode") {
        // Restore state from saved graph
    }
},

registerCustomNodes — Register additional node types

registerCustomNodes(app) {
    // Register custom LiteGraph node types
},

beforeRegisterVueAppNodeDefs — Modify node defs before Vue registration

beforeRegisterVueAppNodeDefs(defs, app) {
    // Modify definitions before they reach the Vue app
},

beforeConfigureGraph / afterConfigureGraph

async beforeConfigureGraph(graphData, missingNodeTypes, app) {
    // Before graph data is applied
},
async afterConfigureGraph(missingNodeTypes, app) {
    // After graph is fully configured
},

getSelectionToolboxCommands — Add commands to selection toolbox

getSelectionToolboxCommands(selectedItem) {
    // Return array of command IDs to show when item is selected
    return ["my.ext.doSomething"];
},

Authentication Hooks

onAuthUserResolved(user, app) {
    // Fires when user authentication resolves
},
onAuthTokenRefreshed() {
    // Fires when auth token is refreshed
},
onAuthUserLogout() {
    // Fires when user logs out
},

Custom Widgets

Adding DOM Widgets

beforeRegisterNodeDef(nodeType, nodeData, app) {
    if (nodeData.name === "MyNode") {
        const origOnCreated = nodeType.prototype.onNodeCreated;
        nodeType.prototype.onNodeCreated = function () {
            origOnCreated?.apply(this, arguments);

            const container = document.createElement("div");
            container.innerHTML = `<input type="color" value="#ff0000">`;
            container.querySelector("input").addEventListener("change", (e) => {
                this.widgets.find(w => w.name === "color").value = e.target.value;
            });

            this.addDOMWidget("colorPicker", "custom", container, {
                serialize: true,
                getValue() { return container.querySelector("input").value; },
                setValue(v) { container.querySelector("input").value = v; },
            });
        };
    }
},

Widget Hooks

// Called before prompt is queued
widget.beforeQueued = function () {
    // Prepare widget value
};

// Called after prompt is queued
widget.afterQueued = function () {
    // Reset or update widget
};

// Custom serialization
widget.serializeValue = function (node, index) {
    return JSON.stringify(this.value);
};

Declarative Extension Properties

Commands

app.registerExtension({
    name: "my.ext",
    commands: [
        {
            id: "my.ext.doSomething",
            label: "Do Something",
            icon: "pi pi-bolt",
            function: () => { console.log("Executed!"); },
        },
    ],
});

Keybindings

keybindings: [
    {
        commandId: "my.ext.doSomething",
        combo: { key: "d", ctrl: true, shift: true },
    },
],

Settings

settings: [
    {
        id: "my.ext.mySetting",
        name: "My Setting",
        type: "boolean",
        defaultValue: true,
        onChange: (value) => { console.log("Setting changed:", value); },
    },
    {
        id: "my.ext.mode",
        name: "Processing Mode",
        type: "combo",
        options: ["fast", "quality", "balanced"],
        defaultValue: "balanced",
    },
],

Setting types: boolean, number, slider, knob, combo, radio, text, image, color, url, hidden, backgroundImage

Sidebar Tabs

async setup(app) {
    app.extensionManager.registerSidebarTab({
        id: "my-sidebar",
        title: "My Panel",
        icon: "pi pi-cog",
        type: "custom",
        render: (container) => {
            container.innerHTML = "<h3>My Custom Panel</h3>";
        },
        destroy: () => {
            // Cleanup
        },
    });
},

Bottom Panel Tabs

bottomPanelTabs: [
    {
        id: "my-panel",
        title: "My Panel",
        type: "custom",
        render: (container) => {
            container.innerHTML = "<div>Panel content</div>";
        },
    },
],

Menu Commands

menuCommands: [
    {
        path: ["My Extension"],
        commands: ["my.ext.doSomething"],
    },
],

About Page Badges

aboutPageBadges: [
    { label: "v1.0.0", url: "https://github.com/...", icon: "pi pi-github", severity: "warn" },
    // severity is optional: "danger" | "warn"
],

Top Bar Badges

topbarBadges: [
    {
        text: "My Extension",        // required
        label: "BETA",               // optional badge label
        variant: "info",             // "info" | "warning" | "error"
        icon: "pi pi-star",          // optional icon
        tooltip: "Extension info",   // optional tooltip
    },
],

Action Bar Buttons

actionBarButtons: [
    {
        icon: "pi pi-bolt",           // required
        label: "My Action",           // optional label
        tooltip: "Run my action",     // optional tooltip
        onClick: () => { /* ... */ },  // required click handler
    },
],

API Events

Listen to execution events:

// Node execution completed
app.api.addEventListener("executed", ({ detail }) => {
    const { node, output } = detail;
    // output contains images, text, etc.
});

// Execution progress
app.api.addEventListener("progress", ({ detail }) => {
    const { value, max, node } = detail;
});

// Execution started/completed
app.api.addEventListener("execution_start", ({ detail }) => {});
app.api.addEventListener("execution_success", ({ detail }) => {});
app.api.addEventListener("execution_error", ({ detail }) => {});

// Status updates
app.api.addEventListener("status", ({ detail }) => {
    const { exec_info } = detail;
});

Server-to-Client Communication

Python (server side):

from server import PromptServer

PromptServer.instance.send_sync(
    "my_extension.update",
    {"status": "complete", "data": result}
)

JavaScript (client side):

app.api.addEventListener("my_extension.update", ({ detail }) => {
    console.log("Received:", detail);
});

Toast Notifications

app.extensionManager.toast.add({
    severity: "info",  // "success", "info", "warn", "error"
    summary: "Title",
    detail: "Message content",
    life: 3000,  // auto-dismiss after ms
});

Dialogs

// Confirmation dialog
const result = await app.extensionManager.dialog.confirm({
    title: "Confirm Action",
    message: "Are you sure?",
});

// Prompt dialog
const value = await app.extensionManager.dialog.prompt({
    title: "Enter Value",
    message: "Provide a name:",
    defaultValue: "default",
});

Context Menu Items

app.registerExtension({
    name: "my.ext",

    // Canvas right-click menu
    getCanvasMenuItems(canvas) {
        return [{
            content: "My Action",
            callback: () => { console.log("Canvas menu clicked"); },
        }];
    },

    // Node right-click menu
    getNodeMenuItems(node) {
        if (node.comfyClass === "MyNode") {
            return [{
                content: "Custom Action",
                callback: () => { console.log("Node:", node.id); },
            }];
        }
        return [];
    },
});

Node Instance Properties (LGraphNode Augmentations)

// Available on node instances:
node.comfyClass       // ComfyUI node type name
node.isVirtualNode    // true for frontend-only nodes
node.imgs             // preview images array
node.imageIndex       // current preview image index

// Callbacks:
node.onExecuted = function(output) { /* execution result */ };
node.onExecutionStart = function() { /* about to execute */ };
node.onDragOver = function(event) { /* file drag over */ };
node.onDragDrop = function(event) { /* file dropped */ };

Frontend Scripts API

Custom node JavaScript can import from the frontend's src/scripts/ modules. Imports use the Vite shim pattern:

import { app } from "../../scripts/app.js";
import { api } from "../../scripts/api.js";

Symbols are also accessible via window.comfyAPI.<module>.<export>.

Stability Levels

Key Modules

• scripts/api — ComfyApi class: fetchApi(), queuePrompt(), getNodeDefs(), WebSocket events, settings, user data, system stats
• scripts/app — ComfyApp singleton (app): graph operations, registerExtension(), extensionManager, clipboard, coordinate conversion
• scripts/widgets — ComfyWidgets registry (INT, FLOAT, STRING, BOOLEAN, COMBO, IMAGEUPLOAD, etc.), addValueControlWidgets()
• scripts/domWidget — addDOMWidget(), DOMWidgetImpl, ComponentWidgetImpl (Vue component wrapper)
• scripts/utils — clone(), addStylesheet(), uploadFile(), downloadBlob(), storage helpers
• scripts/pnginfo — getPngMetadata(), getWebpMetadata(), importA1111(), format-specific extractors

For full API details, see the API Reference.

See Also

• comfyui-node-basics - Backend node structure
• comfyui-node-packaging - Project structure with JS extensions
• comfyui-node-inputs - Backend input types