Pascal online compiler

What runs your code

Good to know

• Compiles with fpc -O2 in Free Pascal's default mode. Add {$mode objfpc}{$H+} or {$mode delphi} for classes and Delphi syntax.
• readln reads from the Input tab. Without {$H+}, string holds at most 255 characters.
• Compiler errors and warnings are shown; notes and hints are not.

Run Pascal 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": "fpc-3.2",
    "code": "program Hello;\nvar name: string;\nbegin\n  readln(name);\n  writeln('\''Hello, '\'', name, '\''!'\'');\nend.",
    "input": "Ada"
  }'

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

Put a runnable Pascal 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="fpc-3.2">
  <script type="text/plain">
    program Hello;
    var name: string;
    begin
      readln(name);
      writeln('Hello, ', name, '!');
    end.
  </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, Octave, Assembly, Lua, OCaml, Common Lisp, Erlang, Elixir, Prolog, D, FreeBASIC, Dart, Clojure, Groovy, Scala, Zig, Nim, Crystal, Ada, PowerShell, Racket, Objective-C.

Frequently asked questions

Is this Pascal online compiler free?

Yes. Running Pascal on this page needs no account and shows no ads. To run Pascal 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 Pascal 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 Pascal libraries?

Free Pascal's runtime library, including SysUtils, Classes, Math and StrUtils. Other units can't be installed, 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.