Online C++ Compiler

main.cpp
// Online C++ compiler (C++17)
// Write your code here and press Run.

#include <iostream>
#include <vector>

int main() {
    std::cout << "Hello, World!" << std::endl;

    std::vector<int> squares;
    for (int i = 1; i <= 3; i++) {
        squares.push_back(i * i);
    }
    for (int s : squares) {
        std::cout << "Square: " << s << std::endl;
    }

    // Tip: to give your program keyboard input,
    // type the values in the Input box below the output.
    return 0;
}
Output

Output will appear here. Press Run or Ctrl + Enter.

Ready

About this C++ compiler

This free online C++ compiler lets you write, compile and run C++17 programs without installing anything. Type your code, press Run, and the output appears beside the editor.

A C++ compiler compiled to WebAssembly runs inside your browser, so there is no account to create and your code is not sent to a server. It is a quick way to try the standard library, practise for a course or a contest, or check a snippet.

How to use it

  1. Write or paste your C++ program in the editor. It needs a main function.
  2. If your program reads input with cin or getline, type the values in the Input box below the output, one per line, in the order the program asks for them.
  3. Press Run (or Ctrl + Enter). The first run downloads the compiler (about 19 MB, saved by your browser afterwards) and compiling C++ takes a moment.
  4. Compiler errors and warnings show the line number, and your program's output follows.

Features

  • Compiles C++17 with clang, entirely in your browser
  • The standard library: vector, map, string, algorithm, memory and more
  • #include <bits/stdc++.h> works, which is handy for contest code
  • Input through the Input box, read with cin, getline or scanf
  • Clear compiler errors and warnings with line numbers
  • Dark and light themes, automatic saving, download as .cpp

Good to know

Frequently asked questions

Which C++ standard is used?

C++17, compiled with clang. Features from C++20 such as concepts and ranges are not available.

Why do try and catch not work?

The browser-based compiler does not support C++ exceptions yet. Use return values or error codes instead. A program that throws will stop with a crash message.

How do I give my C++ program input?

Type the values into the Input box below the output, one per line, then press Run. cin, getline and scanf read from it.

Can I use #include <bits/stdc++.h>?

Yes. It is provided so code written for competitive programming runs unchanged.

Is it free?

Yes. There is no sign-up, and nothing is executed on our servers.

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