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memoryjs · GitHub license npm version

memoryjs is an NPM package for reading and writing process memory! (finally!)

NOTE: version 3 of this library introduces breaking changes that are incompatible with previous versions. The notable change is that when reading memory, writing memory and pattern scanning you are required to pass the handle through for the process (that is returned from memoryjs.openProcess). This allows for multi-process support.


  • List all open processes
  • List all modules associated with a process
  • Find a specific module within a process
  • Read process memory
  • Write process memory
  • Read buffers from memory
  • Write buffer to memory
  • Change memory protection
  • Reserve/allocate, commit or change regions of memory
  • Fetch a list of memory regions within a process
  • Pattern scanning
  • Execute a function within a process
  • Hardware breakpoints (find out what accesses/writes to this address etc)

Functions that this library directly exposes from the WinAPI:


  • WriteFile support (for driver interactions)
  • DLL injections


This is a Node add-on (last tested to be working on v8.11.3) and therefore requires node-gyp to use.

You may also need to follow these steps.

npm install memoryjs

When using memoryjs, the target process should match the platform architecture of the Node version running. For example if you want to target a 64 bit process, you should try and use a 64 bit version of Node.

You also need to recompile the library and target the platform you want. Head to the memoryjs node module directory, open up a terminal and to run the compile scripts, type:

npm run build32 if you want to target 32 bit processes

npm run build64 if you want to target 64 bit processes

Node Webkit / Electron

If you are planning to use this module with Node Webkit or Electron, take a look at Liam Mitchell's build notes here.



const memoryjs = require('memoryjs');
const processName = "csgo.exe";


Open a process (sync):

const processObject = memoryjs.openProcess(processIdentifier);

Open a process (async):

memoryjs.openProcess(processIdentifier, (error, processObject) => {


Get all processes (sync):

const processes = memoryjs.getProcesses();

Get all processes (async):

memoryjs.getProcesses((error, processes) => {


See the Documentation section of this README to see what a process object looks like.


Find a module (sync):

const module = memoryjs.findModule(moduleName, processId);

Find a module (async):

memoryjs.findModule(moduleName, processId, (error, module) => {


Get all modules (sync):

const modules = memoryjs.getModules(processId);

Get all modules (async):

memoryjs.getModules(processId, (error, modules) => {


See the Documentation section of this README to see what a module object looks like.


Read from memory (sync):

const value = memoryjs.readMemory(handle, address, dataType);

Read from memory (async):

memoryjs.readMemory(handle, address, dataType, (error, value) => {


Read buffer from memory (sync):

const buffer = memoryjs.readBuffer(handle, address, size);

Read buffer from memory (async):

memoryjs.readBuffer(handle, address, size, (error, buffer) => {


Write to memory:

memoryjs.writeMemory(handle, address, value, dataType);

Write buffer to memory:

memoryjs.writeBuffer(handle, address, buffer);

Fetch memory regions (sync):

const regions = memoryjs.getRegions(handle);

Fetch memory regions (async):

memoryjs.getRegions(handle, (regions) => {


See the Documentation section of this README to see what values dataType can be.


Set protection of memory:

const oldProtection = memoryjs.virtualProtectEx(handle, address, size, protection);

See the Documentation section of this README to see what values protection can be.

Pattern Scanning:

Pattern scanning (sync):

const offset = memoryjs.findPattern(handle, moduleName, signature, signatureType, patternOffset, addressOffset);

Pattern scanning (async):

memoryjs.findPattern(handle, moduleName, signature, signatureType, patternOffset, addressOffset, (error, offset) => {


Function Execution:

Function execution (sync):

const result = memoryjs.callFunction(handle, args, returnType, address);

Function execution (async):

memoryjs.callFunction(handle, args, returnType, address, (error, result) => {


Click here to see what a result object looks like. Clicklick here for details about how to format the arguments and the return type.

Hardware Breakpoints

Attach a debugger:

const success = memoryjs.attatchDebugger(processId, exitOnDetatch);

Detatch debugger:

const success = memoryjs.detatchDebugger(processId);

Wait for debug devent:

const success = memoryjs.awaitDebugEvent(hardwareRegister, millisTimeout);

Handle debug event:

const success = memoryjs.handleDebugEvent(processId, threadId);

Set a hardware breakpoint:

const success = memoryjs.setHardwareBreakpoint(processId, address, hardwareRegister, trigger, length);

Remove a hardware breakpoint:

const success = memoryjs.removeHardwareBreakpoint(processId, hardwareRegister);


Note: this documentation is currently being updated, refer to the Wiki for more information.

Process Object:

{ dwSize: 304,
  th32ProcessID: 10316,
  cntThreads: 47,
  th32ParentProcessID: 7804,
  pcPriClassBase: 8,
  szExeFile: "csgo.exe",
  modBaseAddr: 1673789440,
  handle: 808 }

The handle and modBaseAddr properties are only available when opening a process and not when listing processes.

Module Object:

{ modBaseAddr: 468123648,
  modBaseSize: 80302080,
  szExePath: 'c:\\program files (x86)\\steam\\steamapps\\common\\counter-strike global offensive\\csgo\\bin\\client.dll',
  szModule: 'client.dll',
  th32ProcessID: 10316 }

Result Object:

{ returnValue: 1.23,
  exitCode: 2 }

The returnValue is the value returned from the function that was called. exitCode is the termination status of the thread.

Data Type:

When using the write or read functions, the data type (dataType) parameter can either be a string and be one of the following:

"byte", "int", "int32", "uint32", "int64", "uint64", "dword", "short", "long", "float", "double", "bool", "boolean", "ptr", "pointer", "str", "string", "vec3", "vector3", "vec4", "vector4"

or can reference constants from within the library:

memoryjs.BYTE, memoryjs.INT, memoryjs.INT32, memoryjs.UINT32, memoryjs.INT64, memoryjs.UINT64, memoryjs.DWORD, memoryjs.SHORT, memoryjs.LONG, memoryjs.FLOAT, memoryjs.DOUBLE, memoryjs.BOOL, memoryjs.BOOLEAN, memoryjs.PTR, memoryjs.POINTER, memoryjs.STR, memoryjs.STRING, memoryjs.VEC3, memoryjs.VECTOR3, memoryjs.VEC4, memoryjs.VECTOR4

This is simply used to denote the type of data being read or written.

Vector3 is a data structure of three floats:

const vector3 = { x: 0.0, y: 0.0, z: 0.0 };
memoryjs.writeMemory(address, vector3);

Vector4 is a data structure of four floats:

const vector4 = { w: 0.0, x: 0.0, y: 0.0, z: 0.0 };
memoryjs.writeMemory(address, vector4);

Generic Structures:

If you have a structure you want to write to memory, you can use buffers. For an example on how to do this, view the buffers example.

To write a structure to memory, you can use the concentrate library to describe the structure as a buffer and then write the buffer to memory using the writeBuffer function.

To read a structure from memory, you will need to read a buffer from memory using the readBuffer function, and then you can use the dissolve library to parse the buffer into a structure.

In either case you don't need to use the two libraries mentioned above, they just make it easy to turn your structure into a buffer, and your buffer into a structure.

Protection Type:

Protection type is a bit flag DWORD value.

This parameter should reference a constant from the library:


Refer to MSDN's Memory Protection Constants for more information.

Memory Allocation Type:

Memory allocation type is a bit flag DWORD value.

This parameter should reference a constat from the library:

memoryjs.MEM_COMMIT, memoryjs.MEM_RESERVE, memoryjs.MEM_RESET, memoryjs.MEM_RESET_UNDO

Refer to MSDN's VirtualAllocEx documentation for more information.


You can use this library to read either a "string", or "char*" and to write a string.

In both cases you want to get the address of the char array:

std::string str1 = "hello";
std::cout << "Address: 0x" << hex << (DWORD) str1.c_str() << dec << std::endl;

char* str2 = "hello";
std::cout << "Address: 0x" << hex << (DWORD) str2 << dec << std::endl;

From here you can simply use this address to write and read memory.

There is one caveat when reading a string in memory however, due to the fact that the library does not know how long the string is, it will continue reading until it finds the first null-terminator. To prevent an infinite loop, it will stop reading if it has not found a null-terminator after 1 million characters.

One way to bypass this limitation in the future would be to allow a parameter to let users set the maximum character count.

Signature Type:

When pattern scanning, flags need to be raised for the signature types. The signature type parameter needs to be one of the following:

0x0 or memoryjs.NORMAL which denotes a normal signature.

0x1 or memoryjs.READ which will read the memory at the address.

0x2 or memoryjs.SUBSTRACT which will subtract the image base from the address.

To raise multiple flags, use the bitwise OR operator: memoryjs.READ | memoryjs.SUBTRACT.

Function Execution:

Remote function execution works by building an array of arguments and dynamically generating shellcode that is injected into the target process and executed, for this reason crashes may occur.

To call a function in a process, the callFunction function can be used. The library supports passing arguments to the function and need to be in the following format:

[{ type: T_INT, value: 4 }]

The library expects the arguments to be an array of objects where each object has a type which denotes the data type of the argument, and a value which is the actual value of the argument. The various supported data types can be found below.

memoryjs.T_VOID = 0x0,
memoryjs.T_STRING = 0x1,
memoryjs.T_CHAR = 0x2,
memoryjs.T_BOOL = 0x3,
memoryjs.T_INT = 0x4,
memoryjs.T_DOUBLE = 0x5,
memoryjs.T_FLOAT = 0x6,

When using callFunction, you also need to supply the return type of the function, which again needs to be one of the above values.

For example, given the following C++ function:

int add(int a, int b) {
    return a + b;

You would call this function as so:

const args = [{
    type: memoryjs.T_INT,
    value: 2,
}, {
    type: memoryjs.T_INT,
    value: 5,
const returnType = T_INT;

> memoryjs.callFunction(handle, args, returnType, address);
{ returnValue: 7, exitCode: 7 }

See the result object documentation for details on what callFunction returns.

Notes: currently passing a double as an argument is not supported, but returning one is.

Much thanks to the various contributors that made this feature possible.

Hardware Breakpoints:

Hardware breakpoints work by attaching a debugger to the process, setting a breakpoint on a certain address and declaring a trigger type (e.g. breakpoint on writing to the address) and then continuously waiting for a debug event to arise (and then consequently handling it).

This library exposes the main functions, but also includes a wrapper class to simplify the process. For a complete code example, checkout our debugging example.

When setting a breakpoint, you are required to pass a trigger type:

  • memoryjs.TRIGGER_ACCESS - breakpoint occurs when the address is accessed
  • memoryjs.TRIGGER_WRITE - breakpoint occurs when the address is written to

Do note that when monitoring an address containing a string, the size parameter of the setHardwareBreakpoint function should be the length of the string. When using the Debugger wrapper class, the wrapper will automatically determine the size of the string by attempting to read it.

To summarise:

  • When using the Debugger class:

    • No need to pass the size parameter to setHardwareBreakpoint
    • No need to manually pick a hardware register
    • Debug events are picked up via an event listener
    • setHardwareBreakpoint returns the register that was used for the breakpoint
  • When manually using the debugger functions:

    • The size parameter is the size of the variable in memory (e.g. int32 = 4 bytes). For a string, this parameter is the length of the string
    • Manually need to pick a hardware register (via memoryjs.DR0 through memoryhs.DR3). Only 4 hardware registers are available (some CPUs may even has less than 4 available). This means only 4 breakpoints can be set at any given time
    • Need to manually wait for debug and handle debug events
    • setHardwareBreakpoint returns a boolean stating whether the operation as successful

For more reading about debugging and hardware breakpoints, checkout the following links:

Using the Debugger Wrapper

The Debugger wrapper contains these functions you should use:

class Debugger {
  attatch(processId, killOnDetatch = false);
  setHardwareBreakpoint(processId, address, trigger, dataType);
  removeHardwareBreakpoint(processId, register);
  1. Attach the debugger
const hardwareDebugger = memoryjs.Debugger;
  1. Set a hardware breakpoint
const address = 0xDEADBEEF;
const trigger = memoryjs.TRIGGER_ACCESS;
const dataType = memoryjs.INT;
const register = hardwareDebugger.setHardwareBreakpoint(processId, address, trigger, dataType);
  1. Create an event listener for debug events (breakpoints)
// `debugEvent` event emission catches debug events from all registers
hardwareDebugger.on('debugEvent', ({ register, event }) => {
  console.log(`Hardware Register ${register} breakpoint`);

// You can listen to debug events from specific hardware registers
// by listening to whatever register was returned from `setHardwareBreakpoint`
hardwareDebugger.on(register, (event) => {

When Manually Debugging

  1. Attatch the debugger
const hardwareDebugger = memoryjs.Debugger;
  1. Set a hardware breakpoint (determine which register to use and the size of the data type)
// available registers: DR0 through DR3
const register = memoryjs.DR0;
// int = 4 bytes
const size = 4;

const address = 0xDEADBEEF;
const trigger = memoryjs.TRIGGER_ACCESS;
const dataType = memoryjs.INT;

const success = memoryjs.setHardwareBreakpoint(processId, address, register, trigger, size);
  1. Create the await/handle debug event loop
const timeout = 100;

setInterval(() => {
  // `debugEvent` can be null if no event occurred
  const debugEvent = memoryjs.awaitDebugEvent(register, timeout);

  // If a breakpoint occurred, handle it
  if (debugEvent) {
    memoryjs.handleDebugEvent(debugEvent.processId, debugEvent.threadId);
}, timeout);

Note: a loop is not required, e.g. no loop required if you want to simply wait until the first detection of the address being accessed or written to.

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