0x is a single-command flamegraph profiling tool for Node.js applications that enables developers to discover bottlenecks and hot paths in their code through interactive visualizations. It offers cross-platform compatibility with automatic stack trace collection and browser-based flamegraph visualization, supports both development and production server profiling scenarios, and includes advanced features like kernel tracing for native stack frames.
npm install -g 0xconst zeroEks = require('0x');For CLI usage as a global binary:
0x [flags] -- node [nodeFlags] script.js [scriptFlags]Profile a Node.js application and generate interactive flamegraph:
# Basic profiling
0x my-app.js
# Open flamegraph in browser automatically
0x -o my-app.js
# Profile with load testing on first opened port
0x -P 'autocannon localhost:$PORT' my-app.js
# Use custom node executable
0x -- /path/to/node my-app.jsconst zeroEks = require('0x');
async function profileApp() {
// Basic profiling - generates flamegraph HTML file
const flamegraphPath = await zeroEks({
argv: ['my-app.js'],
open: true
});
// Data collection only - returns folder path
const dataFolder = await zeroEks({
argv: ['my-app.js'],
collectOnly: true,
outputDir: './profiling-{timestamp}'
});
}0x is built around several key components:
zeroEks for scripted profiling workflowsMain API function for integrating flamegraph profiling into Node.js applications and tooling workflows.
/**
* Profile a Node.js process and generate flamegraph visualization
* @param args - Profiling configuration options
* @returns Promise resolving to flamegraph file path or data folder path
*/
function zeroEks(args: ProfilingOptions): Promise<string>;
interface ProfilingOptions {
/** Command line arguments for target process (required) */
argv: string[];
/** Output name prefix for generated files */
name?: string;
/** Flamegraph title */
title?: string;
/** Only collect profiling data, don't generate flamegraph */
collectOnly?: boolean;
/** Visualize existing profiling data from folder path */
visualizeOnly?: string;
/** Visualize existing V8 CPU profile from file path */
visualizeCpuProfile?: string;
/** Use Linux kernel tracing instead of V8 profiling */
kernelTracing?: boolean;
/** Delay before starting data collection (milliseconds) */
collectDelay?: number;
/** Working directory for profiling operations */
workingDir?: string;
/** Output directory pattern with template variables */
outputDir?: string;
/** Output HTML file pattern with template variables */
outputHtml?: string;
/** Automatically open flamegraph in browser */
open?: boolean;
/** Path to Node.js binary to profile */
pathToNodeBinary?: string;
/** Command or function to execute when port is detected */
onPort?: string | ((port: number, callback: Function) => void);
/** Enable frame mapping for better stack trace resolution */
mapFrames?: boolean;
/** Generate debug tree data file */
treeDebug?: boolean;
/** Write raw tick data to file */
writeTicks?: boolean;
/** Callback function for process exit events */
onProcessExit?: Function;
/** Status reporting callback function */
status?: Function;
}Comprehensive CLI tool providing single-command profiling with extensive configuration options for development and production use cases.
# Basic command structure
0x [flags] -- node [nodeFlags] script.js [scriptFlags]
# Key flags
-o, --open # Open flamegraph in browser
-D, --output-dir DIR # Output directory pattern
-F, --output-html FILE # Output HTML file pattern
-P, --on-port CMD # Command to run when port detected
--collect-only # Only collect data, don't generate flamegraph
--visualize-only DIR # Visualize existing profiling data
--kernel-tracing # Use Linux kernel tracing
--collect-delay MS # Delay before collection starts