Writing Your First Roblox External

A minimal external that reads the current player count and the local player's username, displays them in a terminal, and updates every second. We won't build a full overlay or a working ESP — the focus here is the patterns. Once those are in your hands, what you point them at is up to you.

We'll cover, in order: picking a language, opening the Roblox process, finding the module base, reading values at known offsets, walking a pointer chain, and looping the whole thing into a per-second refresh.

Three reasonable choices:

• C++ — the traditional pick. Direct Win32 access, no FFI overhead, mature ecosystem (ImGui, Direct3D, etc). Steepest learning curve.
• C# — friendly P/Invoke for Win32 APIs, faster iteration than C++, runs on .NET so distribution is trivial.
• Python —pymem and ctypes wrap the OS APIs cleanly. Slowest of the three at runtime, but you'll write working code in minutes instead of hours.

For a first external, Python is the right choice. The syntax is forgiving, you don't fight with build systems, and the moment your idea works you can rewrite the hot loop in C++ if you need the performance.

The pymem library wraps the Win32 process APIs in a Pythonic interface. Install it with pip install pymem.

import pymem

pm = pymem.Pymem("RobloxPlayerBeta.exe")
print("Attached to PID", pm.process_id)

module = pymem.process.module_from_name(pm.process_handle, "RobloxPlayerBeta.exe")
base = module.lpBaseOfDll
print(f"Base address: 0x{base:X}")

Three things happened. Pymem(name) finds the Roblox process by executable name and opens a handle with the right read/write permissions. Themodule_from_name call gets metadata about where the main binary lives in memory; itslpBaseOfDll is the address every static offset is relative to.

Once you have the handle and a base address, reading is trivial. pymem has typed read functions for common shapes.

# Read a 32-bit integer at a static offset (example only — real offsets
# change every Roblox update and you'd have to find them yourself)
PLAYER_COUNT_OFFSET = 0x12345678

count = pm.read_int(base + PLAYER_COUNT_OFFSET)
print("Players in server:", count)

# Read a 64-bit pointer
ptr = pm.read_longlong(base + 0xABCDEF0)
print(f"Pointer: 0x{ptr:X}")

# Read a string (length-prefixed in many cases, but here a plain ASCII read)
buffer = pm.read_bytes(ptr, 32)
text = buffer.split(b"\x00", 1)[0].decode("utf-8", errors="replace")
print("Name:", text)

The Python wrappers handle endianness, buffer allocation, and error propagation automatically. Under the hood every one of these is a ReadProcessMemory call.

Most game data isn't at a static offset — it's buried behind several levels of indirection. A pointer chain follows them step by step.

def read_chain(pm, base, offsets):
    """Walk a chain like base -> *(p+off0) -> *(p+off1) -> ... and
    return the address after the final dereference plus the trailing offset."""
    addr = pm.read_longlong(base + offsets[0])
    for off in offsets[1:-1]:
        addr = pm.read_longlong(addr + off)
    return addr + offsets[-1]

# Example chain (offsets are illustrative; real ones differ and change)
chain = [0x12345678, 0x40, 0x28, 0x80]
target = read_chain(pm, base, chain)
print(f"Final address: 0x{target:X}")

# Now you can read whatever is at that address — an int, a float, a Vector3.
walk_speed = pm.read_float(target)
print("WalkSpeed:", walk_speed)

The pattern is: dereference, add the next offset, dereference again, repeat. The last entry in the chain is a final offset that gets added to the pointer without a dereference — that's the field address.

The hard part is figuring out what the chain actually is for the field you want. That's where reverse- engineering tools like Cheat Engine come in: you find a value in the running game, then use the "find what accesses this address" feature to climb the pointer chain back to a stable module base. That process is worth its own article; here we're assuming the chain is already known.

A full external runs continuously, re-reading values every frame or every second and reacting. The loop is the simplest part:

import time

while True:
    try:
        count = pm.read_int(base + PLAYER_COUNT_OFFSET)
        print(f"[{time.strftime('%H:%M:%S')}] Players: {count}")
    except pymem.exception.MemoryReadError:
        print("Memory read failed — Roblox probably closed.")
        break
    time.sleep(1)

The try/except is important. If the user alt-tabs out of Roblox and closes it, your reads start failing — handle the exception and exit cleanly instead of crashing with a stack trace.

For comparison, the equivalent loop in C++ using raw Win32. Same shape, more boilerplate.

#include <windows.h>
#include <psapi.h>
#include <tlhelp32.h>
#include <cstdio>
#include <thread>
#include <chrono>

DWORD findPid(const wchar_t* name) {
    PROCESSENTRY32W e{ sizeof(e) };
    HANDLE snap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    if (Process32FirstW(snap, &e)) {
        do {
            if (wcscmp(e.szExeFile, name) == 0) {
                CloseHandle(snap);
                return e.th32ProcessID;
            }
        } while (Process32NextW(snap, &e));
    }
    CloseHandle(snap);
    return 0;
}

uintptr_t findModuleBase(HANDLE proc, const wchar_t* name) {
    HMODULE mods[1024]; DWORD cb;
    if (EnumProcessModules(proc, mods, sizeof(mods), &cb)) {
        for (DWORD i = 0; i < cb / sizeof(HMODULE); ++i) {
            wchar_t mn[MAX_PATH];
            GetModuleBaseNameW(proc, mods[i], mn, MAX_PATH);
            if (wcscmp(mn, name) == 0) return (uintptr_t)mods[i];
        }
    }
    return 0;
}

int main() {
    DWORD pid = findPid(L"RobloxPlayerBeta.exe");
    HANDLE proc = OpenProcess(PROCESS_VM_READ, FALSE, pid);
    uintptr_t base = findModuleBase(proc, L"RobloxPlayerBeta.exe");

    while (true) {
        int32_t count = 0;
        ReadProcessMemory(proc, (void*)(base + 0x12345678), &count, sizeof(count), nullptr);
        printf("players: %d\n", count);
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }
}

More lines of code, more types to keep straight, but the conceptual shape is identical. If the Python version is fast enough for your use case (and at 1–60Hz it almost always is), there's no reason to switch.

A printed terminal isn't useful for most external features. The natural next step is a transparent overlay window drawn on top of the Roblox window. In Python the easiest path is tkinter with always-on-top and transparency, or for higher fidelity pyglet / arcade with a borderless window.

import tkinter as tk

root = tk.Tk()
root.overrideredirect(True)               # no title bar
root.wm_attributes("-topmost", True)      # always on top
root.wm_attributes("-transparentcolor", "magenta")  # magenta becomes click-through
root.configure(bg="magenta")
root.geometry("400x100+50+50")            # 400x100 window at (50, 50)

label = tk.Label(root, text="Players: ?", fg="lime", bg="black", font=("Consolas", 18))
label.pack()

def refresh():
    try:
        count = pm.read_int(base + PLAYER_COUNT_OFFSET)
        label.config(text=f"Players: {count}")
    except Exception:
        label.config(text="Players: -")
    root.after(500, refresh)

refresh()
root.mainloop()

A few real overlays are exactly this — a small label updating from a memory read, drawn over the game. For anything fancier (ESP boxes following players in screen-space), you graduate to a real graphics library, but the read-memory-then-draw pattern is the same.

• Cache aggressively. Pointer walks are the slow part — once you've walked a chain and got a final address, reuse it as long as it stays valid. Don't walk from base every read.
• Validate before using. Memory you read might be stale or zero-initialised. Check that pointers are non-null and floats are in sensible ranges before using them.
• Rate-limit your refreshes. 60Hz reads on dozens of pointer chains is more memory traffic than you think. For UI-grade externals, 30Hz or even 10Hz is usually plenty.
• Handle process death. Roblox closing is the most common cause of failed reads. Catch the exception and re-attach on the next launch instead of crashing.
• Maintain your offsets. Every Roblox update potentially breaks every offset you hardcoded. A real external project usually has either an offset-finder tool or a script that re-derives them on each version.

A working external is fewer lines of code than people assume — a few dozen, even with overlay. The complexity isn't in the code, it's in keeping the offsets fresh and handling all the ways Roblox can change on you. For the architectural background and the trade-offs versus in-process tools, our externals primer is the companion read.