Zig online compiler

What runs your code

Good to know

• Builds in Debug mode, so safety checks stay on: an index out of bounds or an integer overflow panics with a stack trace that points at the line.
• Zig 0.17's I/O is new: main takes init: std.process.Init, and stdin and stdout are std.Io.File.reader(.stdin(), init.io, &buf) and std.Io.File.writer(.stdout(), init.io, &buf). Flush the writer before main returns, or the output is lost.
• A run takes about 4 seconds, most of it compiling, so even a short program takes that long.

Run Zig from your own code

Send the code and its input to the sync endpoint with an API key, and the output comes back in the response. The API docs cover the async endpoint with callbacks and every response field.

curl -X POST https://api.onlinecompiler.io/api/run-code-sync/ \
  -H "Authorization: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "compiler": "zig-0.17",
    "code": "const std = @import(\"std\");\n\npub fn main(init: std.process.Init) !void {\n    var in_buf: [256]u8 = undefined;\n    var stdin = std.Io.File.reader(.stdin(), init.io, &in_buf);\n    var out_buf: [256]u8 = undefined;\n    var stdout = std.Io.File.writer(.stdout(), init.io, &out_buf);\n    const name = (try stdin.interface.takeDelimiter('\''\\n'\'')) orelse \"\";\n    try stdout.interface.print(\"Hello, {s}!\\n\", .{name});\n    try stdout.interface.flush();\n}",
    "input": "Ada"
  }'

The response has output ("Hello, Ada!\n" here), error, exit_code, time and memory.

Put a runnable Zig example on your site

The editor above is the embeddable widget. Add the script and a div with your widget key, and your readers can edit and run the code without an account:

<script src="https://onlinecompiler.io/widget.js"></script>

<div class="runcode" data-key="YOUR_WIDGET_KEY" data-lang="zig-0.17">
  <script type="text/plain">
    const std = @import("std");

    pub fn main(init: std.process.Init) !void {
        var in_buf: [256]u8 = undefined;
        var stdin = std.Io.File.reader(.stdin(), init.io, &in_buf);
        var out_buf: [256]u8 = undefined;
        var stdout = std.Io.File.writer(.stdout(), init.io, &out_buf);
        const name = (try stdin.interface.takeDelimiter('\n')) orelse "";
        try stdout.interface.print("Hello, {s}!\n", .{name});
        try stdout.interface.flush();
    }
  </script>
</div>

On a platform that takes an iframe but not a script, such as many course sites, use the iframe embed. For Docusaurus, MkDocs, Sphinx and Mintlify, see runnable code examples in docs.

Other languages

Python, C, C++, Java, C#, F#, Go, Rust, PHP, Ruby, Haskell, TypeScript, JavaScript, SQL, Bash, Fortran, Visual Basic, Kotlin, R, Swift, COBOL, Perl, Julia, Pascal, Octave, Assembly, Lua, OCaml, Common Lisp, Erlang, Elixir, Prolog, D, FreeBASIC, Dart, Clojure, Groovy, Scala, Nim, Crystal, Ada, PowerShell, Racket, Objective-C.

Frequently asked questions

Is this Zig online compiler free?

Yes. Running Zig on this page needs no account and shows no ads. To run Zig from your own app or site, the API and the widget are free up to 100,000 runs a month, commercial use included.

Can my Zig program read input?

Yes. Type it in the Input tab before you run, and the program reads it from standard input. The whole input is sent when you press Run, so a program can't ask for more while it runs.

Can I use Zig libraries?

The Zig standard library; allocate with init.gpa or init.arena. Zig 0.17 has no @cImport, so C libraries can't be used. There is no package manager, and programs have no network access.

How long can a program run?

Up to 30 seconds, with 512 MB of memory and 2 CPUs. A program still running at 30 seconds is stopped with exit code 124, and output over 64 KB per stream is cut.

Where does my code run?

On our servers, in a fresh gVisor sandbox with no network access that is deleted when the run ends. Each run is kept in execution history with its output; the security page says what is stored.