What is a REPL?

Type a code snippet and see the result instantly.

REPL stands for Read-Eval-Print Loop. It reads what you type, evaluates it, prints the result, then waits for your next line. Everything you defined so far is still there.

There is no compile step and no project to set up, so it is the fastest way to:

Learn a new language one line at a time
Try a snippet before it goes into your project
Explore a library or check an expression

RRead

>>> price * qtyReads the line you type.

EEval

250 * 4Runs it with your earlier values.

LLoop

>>> Waits for your next line.

PPrint

1000Shows the result straight away.

A Python REPL session

>>> price = 250
>>> qty = 4
>>> price * qty
1000
>>> price * qty + 50
1050

Getting started

Using the C REPL

Read the docs

Source on GitHub

hyperyolo ~ $

Command
.help

What it does
Display brief descriptions of all meta-commands.

Features

Everything you need to go from idea to output

Run and debug in one place

Press Run to compile and execute your file. Choose Debug from the Run menu to step through C, C++, Go, Rust and assembly with gdb.

(gdb) break main.c:5
Breakpoint 1 at main.c, line 5.
(gdb) run
Breakpoint 1, main () at main.c:5
(gdb) print i
$1 = 1

Fork a REPL

Open a second terminal inside the same sandbox. Run a server in one, a client in the other.

tab 1 $ python3 -m http.server 8000
Serving HTTP on 0.0.0.0 port 8000

tab 2 $ curl -sI localhost:8000 | head -1
HTTP/1.0 200 OK

Pair on a live link

Share one link. Your partner sees your terminal, editor and chat, and can type along.

Genie reads your code

Ask why something fails. Genie sees what's in your editor and suggests a fix you can insert in one click.

Why does line 4 raise a TypeError? You're adding a number to a string. Convert it first with str(count).

Practice for interviews

Generate a DSA problem by topic and difficulty, with starter code in your language.

Open practice

Files that stay with you

Create, upload and download files. Sign in and your workspace is waiting next time.

Open your workspace

Languages

Every REPL you reach for

Pick one and it opens in the workspace above, ready to type.

Request a language

.c .cppC / C++cling .goGogointerpreter · yaegi .pyPythonpython3 · 2.7 · IPython .rsRustevcxr .javaJavaJShell .jsJavaScriptin-browser console .mjsNode.jsnode .tsTypeScriptts-node .rbRubyirb .plPerlperli .shBashbash .tclTcltclsh .sqlSQLitesqlite3 .jsonJSONjq-repl .asmAssembly x86rappel

FAQ

Questions, answered

Do I need an account?

No. Start as a guest right away. Guest files are removed an hour after your last visit; sign up free to keep them.

Is it really free?

Yes. OpenREPL is open source under the MIT license. You can support it through GitHub Sponsors.

How long does a session last?

Up to 60 minutes per connection. The terminal shows the time left, and one click starts a new session.

Can someone code with me?

Yes. Press Share and send the link. They see your terminal and editor live and can type along.

Can I use my own files?

Yes. Upload files up to 20 MB, keep up to 50 MB in your workspace, and download it all as a zip.

What can Genie do?

Genie is the AI helper. It reads your editor and terminal, so you can ask why something fails. Its code suggestions show as a diff you accept or reject, with Undo. Open it with Ask Genie or Ctrl+K.

Can Genie do a task for me?

Yes, in Agent mode, for signed-in users. Genie writes code, runs it and reads the output step by step. It asks before it changes your editor, runs your program or types in your terminal, and you can press Stop at any time.

How many Genie requests do I have?

The line under Genie's message box shows how many requests you have left; click it for the refill rate and your Agent tasks this hour. Requests refill by themselves over time, and signed-in users get more.

Does Genie keep working if I close its panel?

Yes. An answer or an Agent task carries on while the panel is closed. The Ask Genie button shows that Genie is working, a green dot when the result is ready, and an amber dot when Genie needs your answer. Open the panel to see it, or to press Stop.

Can Genie explain or fix just part of my code?

Yes. Select the code in the editor and right-click it: Explain, Fix problems, Add comments or Write tests. Changes show as a diff you accept or reject.

Can Genie help me practise without giving the answer?

Yes. On the Practice page the coach gives up to three hints per question, reviews your solution and states its complexity, and never writes the code for you.

Can Genie manage my files?

Yes, in Agent mode. It can open a file in the editor, create, copy, move, rename and delete files and folders in your Files panel. Renaming, moving and deleting are asked about every time.

Why does Debug start paused?

On some servers programs cannot be traced the usual way, so Debug runs yours under QEMU and gdb connects to it. It waits at the first instruction: set your breakpoints, then type c or run. Ctrl+C stops it again.

Can I run it myself?

Yes. Pull the Docker image and run it on your own machine or server. The README on GitHub has the steps.

Your next idea is one click away.

Pick a language and start typing. No install, no account.

Start coding free Or run it on your own machine:

docker run -p 8080:8080 vickeykumar/openrepl:latest -p 8080