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7 Top HTML Questions to Practice for an Interview

Fri Sep 18 2020 by Christina Kopecky

As one the first topics a full stack web developer or web designer learns, Hypertext Markup Language (HTML) is the basis of a website. It is one of the most popular languages to use in the construction of a web page, used by web developers and designers.


A database for every repl

Mon Sep 14 2020 by Sidney Kochman is already the best place to build your apps. But there was a missing piece: where do you store your data?

We’re introducing Database: a fast, free, and easy key-value store that’s built into every repl.


How to Land Your First Job as a Python Developer

Thu Sep 10 2020 by Galina Divakova

Python’s status as one of the world’s most widely used programming languages is well known. Some experts rank it to be at par with JavaScript in terms of simplicity, flexibility, and popularity. Its syntax is so straightforward and easy to read, custom-built software packages written in Python are the most shared in top online repositories. From app development to Google using the language for crawling webpages — Python is everywhere and it’s an exciting time to be a Python Developer.


Fall 2020 Education Update

Sat Sep 5 2020 by Patrick Coleman

Hey teachers! Back to school is here and we've got an update on our education products and pricing.


Top 8 Python TypeErrors (and How to Solve Them)

Wed Sep 2 2020 by James Gallagher

Encountering errors is a natural part of working in computer science. Whether you are a seasoned coding expert or a newbie, seeing some red text in a console accompanied by an error message is an experience that you will have often.


CLUI Command bar and Search

Thu Aug 27 2020 by Moudy Elkammash and Sergei Chestakov

One of the challenges of adding new functionality to any interface is balancing discoverability with visual clutter. We've written before about how a universal command bar can be a great way to expose features without overloading the UI with buttons. This pattern already works well for us in our mobile interface, so now we're bringing it to desktop! Here's a demo of what it looks like:


Prepare for a Python Interview with These 7 Questions

Tue Aug 25 2020 by James Gallagher

How you respond to questions in a technical interview has a massive impact on whether you’re offered a job with an organization. If you can answer technical questions well and explain your reasoning, your chances of being offered a job is greatly improved.


7 Questions to Help You Prepare for a JavaScript Interview

Fri Aug 14 2020 by James Gallagher

Job interviews are stressful enough. Technical interviews take the process a step further. In a technical interview, knowing the answer to a question does not necessarily mean you’ll be able to answer it. You need to know how to articulate the complex technical topics that you’ve mastered.


The role of AI in coding

Sat Aug 8 2020 by Amjad Masad

In the past decade, we've seen an explosion of innovation in AI and machine learning. However, coding itself was barely touched by AI. The most significant example of AI-powered coding tools is editor autocomplete extensions like Kite or Tabnine.


Common Errors Python Beginners Encounter (with Solutions)

Tue Aug 4 2020 by James Gallagher

Like English, Python has its own set of rules. Lines of code have to be written in a certain way, just like how sentences must follow a specific structure. Punctuation must be used within a set of guidelines when you’re writing in both English and Python code.


Language Jam Registration is Open

Sat Aug 1 2020 by Amjad Masad

You can now register your team to enter the programming language jam! In addition to setting up your team you can start brainstorming ideas, but we ask you to wait until the 10th before you start hacking.


Audio - Play sound in any language on the web

Fri Jul 31 2020 by Wade Bourne

Audio brings games and projects to life! Web developers have it easy, they can publish their apps on the web and play audio using the browser API no problem. However, what about those of us that are command-line and graphics apps in other languages? is a special place on the web where you can publish any app in any language, but so far it’s been missing audio capabilities because code executes in a container on the backend. This summer, for my internship I set out to solve this problem and make it possible to play audio in any repl in any language. In this post I’ll show you how to play audio in your repl and then I will chronicle the journey that got us here.


New course - How to teach yourself coding with Quizlet Founder Andrew Sutherland

Wed Jul 29 2020 by Patrick Coleman

Like many of you, we’ve been stuck at home, trying out new hobbies, attempting to learn new things, and anxiously waiting until life “gets back to normal.” Well, regardless of how you’ve been spending your time during COVID, if you (or a friend or family member) have been wanting to learn how to code, we want to help!


Shareable Computing

Wed Jul 29 2020 by GPT-3

This is a guest blogpost by GPT-3, the new AI software from OpenAI. We only gave it the title and "" and it generated the following post for us


A Beginner's Guide to SQL

Tue Jul 28 2020 by James Gallagher

Data is absolutely everywhere. When you visited this web page, you generated data. When you took a note of your to-dos for the day in your reminders, you generated data.


Emmet support

Mon Jul 27 2020 by Amjad Masad

Emmet is a plugin for many popular text editors which greatly improves HTML & CSS workflow, it's also one that's been requested by many of our users.


Dear users coming from Glitch

Thu Jul 23 2020 by Amjad Masad

First, at we're not motivated by competition. What we care about the most is making programming and computing more accessible. That means anyone who wants to code and build things should be able to do so without any hurdles.


The Programming Language Jam & Grant

Tue Jul 21 2020 by Amjad Masad

UPDATE: The jam registration is now open. Read the instructions.


HTML Concepts to Start Your Web Development Journey

Fri Jul 17 2020 by Christina Kopecky, Career Karma


Java Concepts I Wish I Knew Years Ago

Fri Jul 10 2020 by James Gallagher

When I think about the best programming languages to learn, Java is near the top of the list. The language has a wide range of use cases and a beginner-friendly syntax that makes it a great language to learn. While Java may be older than some languages like Ruby or Python, it’s a valuable skill to have if you’re willing to devote the time to learning Java.


CSS Concepts I Wish I Had Known Years Ago

Mon Jul 6 2020 by Christina Kopecky

When I think of web development, I like to think of it in terms of building a house. When we learn HTML, we are learning how to build the web page from the ground up, framing it with the lumber that will eventually become our end product.



Thu Jul 2 2020 by Sergei Chestakov is a great place for prototyping ideas and starting new projects. However as your projects get bigger, the editing experience starts feeling a little limited. That's why we're exciting to announce that we're adding support for tabs!


Teams for Education

Tue Jun 30 2020 by Amjad Masad

We started to break down what we thought of as needless barriers to start coding. Naturally, our first product was the repl -- a simple editor and console for evaluating code. Turns out that’s all our users needed to learn enough coding to make meaningful programs. From there, started to grow incredibly fast among students, developers, and educators. As we watched what our most active users did with the platform, a pattern emerged around coding in the classroom: teachers would prepare a doc or a PDF with instructions and a base repl for their students to fork. Students then would open the PDF side-by-side with the repl and start coding. When finished, they would copy the link and email it back to their teachers. Finally, teachers would block off an afternoon to evaluate and give feedback on their students’ code. The process, while better than using a local IDE and passing around files, seemed tedious and we wanted to solve it -- that’s how Classroom emerged.


Git: An Introduction for Beginners

Mon Jun 29 2020 by James Gallagher

When you’re working on a software project, it’s crucial to keep a log of all the changes made to the project. This will help you see how your work has evolved over time. It will also allow other collaborators on a project to keep track of what changes have been made and by who. That’s where Git comes in.


Community Video Competition

Tue Jun 23 2020 by Patrick Coleman

Over the past week, we ran a video competition for Replers. We got some great submissions from the community, and now it's time to announce the winners!


Popular Beginner JavaScript Concepts

Mon Jun 22 2020 by James Gallagher

JavaScript is behind nearly every modern website on the web. JavaScript powers most of the dynamic features you see on the web, such as buttons which change when they’re clicked or images with zoom capabilities.


Popular Beginner Python Concepts

Mon Jun 15 2020 by James Gallagher

Python is a programming language that’s widely favored by beginners. It’s no wonder, really. Python has a simple syntax which many people say resembles English, so it’s easy to read and write. In addition, Python is used for a wide array of purposes, from data science to web development.

Read more... and GitHub Classroom

Thu May 28 2020 by Tyler Angert & Jeremy Press has always tried to make coding fast, easy, and work seamlessly with your other tools. That’s why we’re excited to announce that has teamed up with GitHub Classroom to make learning how to code even easier.



Fri May 22 2020 by Sergei Chestakov

Oftentimes when we're sharing a repl with a friend we want to link them to exactly where we are in our project. Well now you can with deeplinking!


Terminal Links

Thu Apr 30 2020 by Arnav Bansal

Terminals make it hard to copy things: Selecting text works differently to what people are used to, and ^C aborts the current program. Links are hard to use.


Improving's Mobile UX

Tue Apr 28 2020 by Moudy Elkammash

I like the process of writing because of how simple and portable the tools are. Regardless of time or place, a way to write things down is never far away. There's very little friction between inspiration and experimentation. I wish writing code was more like this.


Bringing's Marketing to the Modern Age

Fri Apr 17 2020 by Tyler Angert


Terminal Search

Tue Apr 14 2020 by Amjad Masad

When you're deep into a debugging session printing a bunch of here, there, and wat, the output in the terminal can get hard to read. That's when search comes in handy, and that's why we're excited to announce our new terminal search functionality.


Packaging Support for Java - Try Maven Packages in Your Browser

Wed Mar 25 2020 by Amjad Masad

Java is one of the most popular languages on, and the JVM powers many of our other languages (Java Swing, Clojure, Kotlin). We want to make it as easy as possible to code with other people and build new programs out of programs that already exist. So we've added packaging support for Java!


Using as a CMS

Mon Mar 23 2020 by Tyler Angert

At, we try to dogfood (use our own product) as much as we can. Parts of are already developed on / hosted entirely on itself-- our blog, our docs, and even our new UI library is being developed almost entirely on But one interesting use case we’re exploring now is using as a CMS for all of our new marketing pages.


How to Conduct Remote Interviews

Fri Mar 20 2020 by Amjad Masad

Remote interviews can be hard, especially if you’ve never done them before. With the COVID-19 crisis, we’re seeing a lot of teams forced to transition to remote interviewing. Luckily, we’ve done hundreds of remote phone screens, and more recently we’ve been doing what we’re calling “remote onsites.” In this post, we'll describe how we and some of our customers leverage Multiplayer -- our realtime collaborative development environment -- and other tools to interview candidates remotely.


Teach Coding Remotely - free for public schools and 80% discount for everyone else

Fri Mar 13 2020 by Amjad Masad

We've been hearing from our teacher community that despite school closings they want to continue teaching their students remotely. Luckily was designed to be remote-first and will be a perfect tool for this. We have two products that serve different remote modes:


CLUI: Building a Graphical Command Line

Thu Mar 5 2020 by Tyler Angert and Moudy Elkammash

“Command line interfaces. Once that was all we had. Then they disappeared, replaced by what we thought was a great advance: GUIs. GUIs were - and still are - valuable, but they fail to scale to the demands of today's systems. So now command line interfaces are back again, hiding under the name of search. Now you see them, now you don't. Now you see them again. And they will get better and better with time: mark my words, that is my prediction for the future of interfaces.” [1]


Repl from Repo

Tue Dec 10 2019 by Amjad Masad

When I think of GitHub I imagine a vast network of people and code; a superorganism that changed how we make software. When I was getting into programming, starting a new project was daunting -- you had to imagine and build everything nearly from scratch. My version of code-sharing was calling my older cousin who was going to college for CS and getting code dictated to me over the phone. When the Internet arrived in my home town, it made hacking on new projects so much more fun. Starting a new project, at least initially, became about discovery:


Open-Sourcing the Universal Package Manager

Wed Oct 30 2019 by Radon Rosborough


Free Hacker Plans for Eligible Students

Tue Sep 24 2019 by Bryan Byrne

We believe everyone should have instant access to a complete coding environment in their browser. That’s why has joined the GitHub Student Developer Pack, giving eligible students free access to private repls, unlimited multiplayer sessions, and additional processing power. Students can now focus on learning and collaborating with their classmates in new ways, without the hassle of setting up a new environment each time.


Making Collaborative at Heart

Wed Sep 18 2019 by Amjad Masad

Coding, people believed, was an activity hackers did alone. While that might have been true in the past, the world is changing. New programmers come online every day and they want to effortlessly work and interact with others while writing code. Yet collaborative coding environments have remained troublesome to setup.


SQLite, replified

Fri Aug 2 2019 by Sidney Kochman

SQLite is now a supported language on! Our SQLite support brings the entire SQLite command-line interface right into your workspace. Now you have a simple way to experiment, prototype, or refine your data model with SQL.


Previewing Markdown in Repls

Fri Aug 2 2019 by Tim Chen

When our community members want to provide instructions within a repl, the most common pattern we've seen is in a .txt file, or as a code comment. Users quickly figured out that while they could make markdown files, there was no way to render it in a more readable format. Today, that changes. We're happy to announce that you can now preview markdown in repls!


Dev Spotlight with Chad Fowler: Build something useless, become a better developer.

Mon Jul 1 2019 by Katya Delaney & Katherine Huang

Last week, Kat and I were lucky enough to sit down with Chad Fowler, programmer, author of The Passionate Programmer, start-up investor, founder of both The International Ruby Conference and RailsConf, and musician.


Adding a language to Emacs Lisp

Mon Jun 24 2019 by Radon Rosborough

At, we want to provide a top-tier online programming experience in as many languages as we can support. Today, we’ll show you just how we do that.


Make coding your jam

Thu Jun 20 2019 by Katherine Huang

Code + music: In tune with each other

Read more... Q&A

Tue May 14 2019 by Katya Delaney

Building tools for a helpful community

“Community” is one of the hardest concepts to define in the English language. Weird, right? It seems like it would be intuitive, but it’s actually something sociologists have struggled with for hundreds of years. Is a community defined by a shared space? A language? A goal? Something as nebulous as just a feeling or an attitude? The answer changes dramatically depending on who you ask.

Read more... GFX: Native graphics development in the browser

Thu Mar 21 2019 by Amjad Masad

At we live and breathe making software creation easier. With our programming environment, you could start coding in your favorite language in seconds. With live deployments, we made web hosting a breeze. With Multiplayer, we've removed the drudgery from coding with friends. And today, we're excited to bring native GUI applications and game development to the browser.

Read more... Multiplayer

Thu Dec 6 2018 by Faris & Amjad Masad

Today we're announcing the most-significant evolution of our platform — something we've been building towards for a long time that we're thrilled to share with you.


Colorizing Stderr: racing pipes, and libc monkey-patching

Fri Nov 2 2018 by Rob Blanckaert

Errors are red,
Outputs are white,
File descriptor injection is bold,
Let me tell you about LD_PRELOAD.

Read more... raises $4.5M, announces a million users

Mon Oct 22 2018 by Amjad Masad

We're thrilled to announce that we have raised a Seed round led by Andreessen Horowitz, with Marc Andreessen and Andrew Chen championing the deal. We're also sharing that a million users are now using Moreover, our developers have shipped 250,000 websites/apps since our hosting platform launch in March.


File Switcher

Tue Oct 16 2018 by Faris Masad

A few days ago we shipped a simple feature that will save our users time in finding and opening files, especially for larger projects. This can even be used without having the file tree visible. Read on to see how to use it and to see a demonstration.


Rejected Then Recruited: Our Journey into Y Combinator

Tue Sep 25 2018 by Amjad Masad

"The intoxicating delight of sudden understanding"1 best describes what I felt the first time I derived the Y Combinator (guided by the Little Schemer book). Learning Lisp (by way of Scheme) is how I first came about Paul Graham's essays. Which was, of course, a gateway drug to startups.


Databases Built by Students

Mon Sep 24 2018 by Nathan Zilora

In case you weren't aware, the discord server recently had a code jam, with the objective being to make a database. Over 14 people finished and submitted a design for the jam. However this jam was a bit different compared to our first and second jams. First of all, we have groups of 2, instead of individual people. This could be viewed and a boon or a bane, but we'll go over that in more detail later. The second set differences were the bonus points. In the past, we've always graded on code quality, efficiency, and creativity.


Bash Shell Experiment

Fri Sep 14 2018 by Rob Blanckaert

Repl's now provide access to an experimental bash shell via the command palette (F1)


Dark Theme Released

Thu Sep 13 2018 by Tim Chen

Dark Theme has long been one of the most highly request features on We introduced a dark theme editor some time back, but as the rest of the workspace was still in " Light Mode", we knew our work wasn't done. We are proud to announce the release of " Dark" - a dark theme for the entire workspace!


Hack Chicago

Fri Aug 10 2018 by Yev Barkalov

On the weekend of July 21st, we sponsored and attended the Midwest's largest high school hackathon, Hack Chicago!


Community-Led Code Jams

Fri Aug 10 2018 by Tim Chen

A few months ago, we created a new Discord channel - a real time chat app - for We've since expanded our user count to be well over 500. Our Discord server is community-driven - we have a team of three users who help us moderate the server and facilitate a culture of friendly collaboration and sharing knowledge. However, our favorite outcome of this community are the code jams.



Thu Jul 26 2018 by Yev Barkalov

Today we're going to learn how to use Firebase as a database for a simple website using JavaScript!


Not Hotdog

Thu Jul 19 2018 by Yev Barkalov

Today we're going to write a program that tells you whether an image is a hotdog or not!


Universal Package Manager

Thu Jul 19 2018 by Amjad Masad

Open-source has revolutionized software development -- it wouldn't be an overstatement to say that it's been the most significant productivity win for developers in the last decade or so. At, our goal is to make programming more accessible and what better way to do that than make available to programmers the entirety of open-source packages available at their fingertips.


July IRL Recap

Mon Jul 16 2018 by Yev Barkalov

On July 11th, we had our second IRL and it was an amazing event!


Zero Setup VSCode Intelligence

Mon Jul 2 2018 by Faris Masad

At our goal is to provide state of the art in developer tools to everyone in the world, for free. When we started moving our product beyond a simple REPL and started adding IDE features, we had to invent standards and wrappers around every language tool for our frontend to consume. For every editor feature, say errors and warnings (linting), we had to extend our development protocol with a set of commands and data structures, and then teach our development containers how to wrap the given tool, say Pylint, and our frontend on how to consume it (say annotate the editor with errors and warnings). A similar thing has been happening with IDEs for the past few decades -- every editor had to come up with their in-house ad-hoc protocol, and every tool developer had to build adapters and wrappers for editors to consume.


Showcase Repls on your Profile

Mon Jul 2 2018 by Tim Chen

As you use more and more, you often find yourself frequently creating repls for quick testing. On your repls dashboard, you can mark important repls by starring them - allowing you to quickly access them. However, there was no way to surface your best work on your profile - users would have to sift through all your repls to find the one they were looking for - until now.

Read more... @ StuyHacks

Wed Jun 27 2018 by Yev Barkalov

I’m still in high school but I just flew from San Francisco to New York City to be a sponsor at a high school hackathon so, yeah, you already know that the whole experience was pretty awesome.


July IRL Info

Wed Jun 27 2018 by Yev Barkalov

For the month of July, our IRL will be taking place on July 11th from 4 to 7 PM at the Bradfield School of Computer Science!


Image Previews with Live Reloading

Fri Jun 15 2018 by Tim Chen

We recently added some changes to how eval mode/project mode operates. These changes allow you to interact with generated files through the console.


First Website Tutorial

Thu Jun 14 2018 by Yev Barkalov

While you can write web applications and text-based ensembles in, sometimes it's nice to be able to just put together a simple HTML/CSS website using the same awesome editor!


React Framework Preboot

Wed Jun 13 2018 by Amjad Masad

Two days ago we introduced our beta support for React frameworks, ranging from static-site generators like GatsbyJS, to fullstack frameworks like Next.js. Today we're launching a significant performance enhancement that we're calling preboot.

Read more... IRL

Wed Jun 13 2018 by Yev Barkalov

On Monday, June 11th, we had our first Meetup and it was super awesome!

Read more... ❤️ React

Thu Jun 7 2018 by Amjad Masad

Despite the negative press covfefe around React.js when it first came out, I instantly fell in love with it. The thing I liked the most about it was the component model. Until then the JavaScript community has been trying for years to come up with the correct abstraction for creating reusable modules, but it was always leaky. Because React components are essentially functions, and because functions are the undisputed champion of reusable code, it worked out extraordinarily well. You don't need dependency-injection, or any other modularity hacks, you simply pass props! Also, the virtual dom made it so that components are, by default, protected from other components prying into their internals.


Don't Let Your Development Environment Rot

Mon Jun 4 2018 by Amjad Masad

Most systems -- both natural and artificial -- decay, rot, and eventually die. Software is no different. A lot has been written about fighting "software rot" but there's another type of rot related to software that's not talked about much -- the development environment rot.


Guest Blog Post: Neural Networks and Primes

Thu May 3 2018 by Ollie Parish

Ollie Parish, also known as @op on, is an avid Repler and constantly pushes our systems to its limits (in the best way). In this guest blog post, he describes his journey in using neural networks to generate large primes. You can also check out the repl described in his research:


A Better Way to Search Your Repls

Mon Mar 19 2018 by Tim Chen

Along with the ability to star repls and tag repls, we now take repl organization one step further with the ability to search through your repls.

Read more... 1.0: the IDE That Grows—from Playgrounds to Fullstack Apps

Tue Mar 13 2018 by Amjad Masad

At we come to work every day to explore a single idea—what if programming just worked? What if instead of fiddling around with packages, configurations, and mismatching versions, you just open your IDE and start coding. What if developers can go from an idea to coding and shipping software with no time in between. What if teachers who want to teach programming don't have to also work as IT administrators. What if students can just code their homework without having to set up the development environment on every computer they wanted to code on.


Live Server Development and Deployment (Beta)

Mon Mar 12 2018 by Amjad Masad is becoming the platform where developers come to learn and build. With web hosting we also made it possible to host websites and since then we've seen an explosion of websites hosted on Today we're going further by making it possible to deploy servers on


File tree!

Fri Mar 9 2018 by Faris Masad

Sometime in 2016 we in introduced the concept of "files" to, you would click add file and a tab would appear on your Repl. As simple repls grew into full fledged applications and websites tabs started getting ugly and hard to manage.


Require Ruby Gems

Thu Mar 8 2018 by Amjad Masad

On the heels of our Node.js npm support announcement, we're pleased to announce that we now support Ruby Gems too. We're excited to have the Ruby community join the fun.


I Built This - Feb 2018 Competition Summary

Thu Mar 8 2018 by Tim Chen

As we released I Built This, our community where users can post about their repl creations, we were exposed to many amazing projects created by our users. To kick it off, we hosted a competition where users post their work and garner upvotes for prizes. The projects shared in the competition spanned a wide range of skill levels, from beginner to advanced, from simple to complex.


Introducing Node.js package support

Wed Mar 7 2018 by Amjad Masad

Ever since we introduced third-party package support for Python we've seen an explosion of exciting programs on Everything from games to machine-learning applications that just weren't possible before.


New and improved repls page

Mon Feb 26 2018 by Amjad Masad

People use in a variety of ways; some use it for building and shipping applications, while others use it for working on homework, and many others use it as a quick prototyping/experimentation tool. Supporting all these use cases (and more) is something we care a lot about, but up until now there wasn't an easy way to, for example, quickly go back to a project that you continue to work on every day.


Modular, fast, small: how we built a server-rendered IDE

Wed Feb 14 2018 by Mason Clayton

At our mission is to make programming more accessible, which means our coding environment needs to be lightweight, load fast, and work from anywhere in the world. However, as with so many software projects that evolve with time, we accumulated some bloat (luckily, we haven't included a mail client yet) and quite a few ad-hoc hacks to glue everything together. In this post, we'll go over how we designed our new IDE to have a small core (everything is a plugin), to be easily customizable (even on the fly), and to server-render.


Internet access for all

Mon Feb 5 2018 by Tim Chen is quickly becoming a tool that's used in everyday programming, and our users are building all sorts of amazing programs. One thing that's been missing for a long time is the ability to access the internet from repls. Being able to call APIs or remote servers is something programmers can't live without. That's why we're excited to announce that starting now we're openning internet access for all!


Pricing update

Mon Feb 5 2018 by Amjad Masad

At our mission is to make programming more accessible. We want to build the platform that will empower the next billion programmers to build the future of software. To accomplish this we needed to build a sustainable business that allows us to grow with our users.


Cloning Assignments

Tue Jan 30 2018 by Tim Chen

You can now copy and clone an assignment from one classroom to another! Many teachers have requested this feature, and we are happy to announce that it has been released!


Teaching refugees how to code

Fri Jan 26 2018 by Haya Odeh

At our mission is to make programming more accessible. We can’t do this alone so it’s great to partner with non-profits and hack clubs that share our mission. Re-coded is one of those non-profits, they're teaching programming in the refugee camps in Iraq and Turkey. Today I’d like to share with you their story of how they found useful in overcoming logistical challenges.


Your websites hosted on

Mon Jan 22 2018 by Amjad Masad

People in our community build awesome games, apps, and websites on's web programming environment, but until now they didn't have any easy way of sharing these creations with other people.


Repl History

Mon Dec 11 2017 by Amjad & Faris Masad

At we focus on simplicity, speed, and, most importantly, reliability. If you're using as your primary or secondary IDE we want you to be confident that the time you invest working on your code will never go to waste.


New in Repls: autosave, custom urls, and more

Sun Nov 12 2017 by Haya Odeh

We are always excited about launching new features and sharing with you, our dear users, what we’ve been up to. For the past few months, Amjad, Mason and I have been working hard and last night we quietly launched the new repl features. These features required a lot of infrastructure and data changes which is always tricky to execute. We ran into some technical difficulties last night with the data migration but was able to bring the site back up and things have been running relatively smoothly since then.


A Few Updates in the Workspace

Fri Sep 8 2017 by Mason Clayton

We strive to make the workspace as useful as possible while keeping it intuitive and approachable. We get a crazy number of requests for features every day, not to mention our own ideas. It becomes a challenging balance between feature creep and simplicity. Lately we've added a few of these features that we hope you'll find useful and, if not, you won't even notice they're there.


Two Stories from Our Community

Wed Aug 23 2017 by Haya Odeh

Like any other startup, we go through ups and downs. However, we try to keep a positive energy, and you, my friends, contribute to that by sending your love, support, and thanks everyday. Above all, you inspire us with stories of how our product helped you learn, teach, and even develop a new skill to land a better job.


Your Profile

Wed Jul 5 2017 by Amjad Masad, Haya Odeh, and Mason Clayton

We're constantly surprised and delighted by the creativity of people in our community. Whether it be games, animations, utilities, or simply snippets to answer Stackoverflow questions -- it's always fascinating to see! However, we haven't done a good job giving credits to authors for their creations.


One more console

Thu Jun 1 2017 by Amjad Masad

Debugging web projects on can be frustrating. Until today, there was no easy way to view your errors and console logs (unless you open your browsers' developer tools). But that's changing because we're introducing our new tabbed console view for environments that has graphics output (like Web and Python Turtle).


Changelog (of imports and turtles)

Tue May 30 2017 by Amjad Masad

Some changes and fixes we make don't deserve their own blogpost. So we thought a good way to keep you up-to-date is to collect however many that could be of interest and write a "Changelog".


Check out my Repl!

Mon May 29 2017 by Haya Odeh

The label "sessions" is very near and dear to my heart. I vividly remember how Amjad came up with the name and why. After we learned that people would like to create accounts on, we were trying to figure out what was the main value proposition for creating an account. Of course, it was saving code! But what do you call a list of code projects saved on your account?


Introducing Kotlin REPL

Thu May 18 2017 by Amjad Masad

On the heels of Google announcing native Kotlin support on Android yesterday, we thought it'd be cool to get a Kotlin REPL up so that people can try it.


React Native

Tue Apr 25 2017 by Alek Hurst

We have discontinued support for react native


Model solutions

Fri Apr 21 2017 by Vitaly Pavlenko

There is a special moment in learning: when a student runs their code against the unit tests and finally sees all of them turn green. This moment of enlightenment means the student has just managed to create their own working solution to a difficult problem, and has made a step towards becoming a great programmer! Wouldn't it be cool to further enhance the student's knowledge by showing the student different approaches to tackle the same problem?


Require any npm package

Tue Mar 28 2017 by Amjad Masad

Last year we introduced support for importing any Python package from PyPi and -- although we don't have perfect support for all packages -- it turned out to be a very popular feature. That's why today we're excited to continue the roll-out for the rest of our platform starting with web-based languages.


Building Towards a Holistic Development Service

Mon Mar 27 2017 by Amjad Masad

Software development is one of the first -- if not the first -- examples of what J. C. Licklider called the Man-Computer Symbiosis. A "cooperative interaction" between people and computers where the person is concerned in what may be classified as the creative aspect of the work such as setting the goals, formulating the hypothesis and evaluating the results while the computer does all the "routinizable work".


YouTube tutorials using

Mon Mar 20 2017 by Amjad Masad

We've been seeing more and more coding video tutorials using YouTube and Today we're sharing some of our favorite YouTube videos that uses


Introducing Clojure

Fri Mar 3 2017 by Amjad Masad

Earlier this week we introduced Haskell support. And now, as promised, we're continuing to add more functional languages. So today we're excited to introduce Clojure. A Lisp dialect that runs on top of the Java Virtual Machine with a focus on immutability.


Introducing Haskell

Mon Feb 27 2017 by Mason Clayton

We heard your requests for Haskell and today we're excited to finally announce Haskell as yet another language we support. We've decided to put our focus on adding more functional languages, starting with Haskell, so you can expect more very soon.


Collaborate with Other Teachers in your Classrooms

Wed Feb 15 2017 by Alek Hurst

Hey teachers, we've noticed that you have been teaching up a storm in your Replit classrooms, and with this feature we want to turn those storms into educational hurricanes! To do so, we implemented teacher collaboration, which allows you to add an additional teacher to your Replit classrooms. This additional teacher can do almost everything you can do, excluding a couple of small destructive things...


Assignment Dependencies

Fri Jan 27 2017 by Haya Odeh

Fundementally, learning is about completing basic material before moving on to more advanced stuff.


Infinite Loops

Mon Jan 23 2017 by Amjad Masad

At we aim to make the full power of programming easily accessible for everyone. That's why when we designed our code execution service we decided that we would not timebox users' programs or sessions.


Assignment Reordering

Thu Jan 19 2017 by Haya Odeh

At our mission is to make programming more accessible, and the best way we found to achieve this is to support, you, the teachers on the ground doing working with students. That's why we want to make sure you control the student experience and today we're making it possible to control the assignments order from your classroom dashboard.


Live File Updates

Fri Dec 23 2016 by Mason Clayton

Today we're excited to release a feature which shows any files your program creates directly inside the REPL. And any time that file changes it will be updated live in the editor. This can be anything from a text file to a gif.


Python Package Search

Fri Dec 2 2016 by Amjad Masad

We recently made it possible to import any package from PyPi. However, people who missed the announcement didn't know this was possible. There was also no good way to search and explore packages.


Introducing Step Debugging for Python

Mon Nov 28 2016 by Amjad Masad

Debug your Python3 programs from your browser

At, our goal is to make programming more accessible, and as part of this we aim to provide the full power of popular programming environments with no setup time. And I don't think it's an understatement to say that debugging is the majority of what we, as programmers, do.


Learning Devops & AWS on the Job: Building and Scaling a Service

Mon Nov 14 2016 by Amjad Masad

Or, what I wish you I knew before building's code execution service


Introducing Pylint Support

Sat Nov 12 2016 by Amjad Masad

Today, we're excited to introduce lint support for Python3. Where previously you had to run your code, look at the console for an error, find the line number of the error and then find that line in your editor. Now, we'll show you errors and potential mistakes live as you type!


from PyPi import *

Tue Oct 25 2016 by Amjad Masad

Import any Python Package

At, our goal is to make programming more accessible, and as part of this we aim to provide the full power of popular programming environments with no setup time. And no modern programming language is complete without third-party packages.


Introducing Turtle Graphics For Python

Tue Oct 4 2016 by Amjad Masad

Ever since the LOGO programming language educators have been using Turtle Graphics to demonstrate the power of programming to their students while making it fun and interesting.


Assignment Due Date

Fri Sep 30 2016 by Faris Masad

On Wednesday we announced assignment scheduling, and today we're releasing another date related feature—due dates. It's no secret that students can procrastinate, so sometimes it's useful to have deadlines for the assignments as a reminder.


Scheduled Assignments

Wed Sep 28 2016 by Amjad Masad

Today, we're introducing scheduled assignments. Teachers using Classroom can now schedule assignments to be published in the future. You can imagine working on your assignment, schedule a publish date, go on vacation, and still have your students receive their assignments at the right time.


Vagueness to Clarity

Thu Jul 28 2016 by Haya Odeh


Simple design is not only how the product looks like, but more importantly, how the product functions; it’s about creating the easiest and simplest path for the user to accomplish their goal. Usually, simple design comes from complex requirements and a lot of ideas — in order to break it down I usually go through a process that I call Vagueness to Clarity


Every Project Should Have Its Own REPL

Thu Jul 21 2016 by Amjad Masad

It's no secret we're big fans of REPLs. We believe that immediate access to the programming environment accelerates learning and is generally more productive. REPLs cut out the middleman -- no need to build UIs or scripts for every possible action you might want to take -- just talk to the interpreter directly.


Evalbot: a bot that speaks code

Sat Jul 2 2016 by Faris Masad

Arguments over programming language semantics, standard library behavior, or syntax can now be simply and immediately settled within the chatroom by talking to Evalbot. It is a bot that can speak over 10 programming languages and is ever-present on Messenger and can be added to your team chat on Slack.


Classroom Overview

Wed Jun 29 2016 by Haya Odeh

Before we decided to build classroom, we paid a visit to one of the schools using us in the classroom. I felt excited and anxious at the same time; I was introduced to the teacher and students in the class, and then my job started as designer observing and paying attention to every single detail.


Distributed Websocket Rate Limiting

Sun Jun 26 2016 by Amjad Masad

Rate limiting is standard practice for services offering an API. It's used for both protecting against bad actors, for example, attempting DOS attacks and to simply enforce limits on the service. There are many resources on the web on how to implement a rate limiter in your favorite language/stack. However, I couldn't find anything on how to rate limit Websocket connections (they differ in that they are persistent connections).


API Docs

Fri Jun 24 2016 by Amjad Masad's code execution API is an HTTP and WebSocket endpoint that you connect to and send code to execute. You can connect from any device or browser and start executing code. This guide will describe the concepts behind the service, how it can be used, and provide a step-by-step guide for signing up and trying out the service!



Sat Jun 18 2016 by Faris Masad

Autocomplete plays a big role in how we use software, imagine a world where you have to type full search terms without predictions into google search, ugh, the savagery! Many developers employ this technology when writing code in order to increase their productivity. So we decided to implement this feature to help you become the power user you want to be.


Hello World

Tue Jun 14 2016 by Amjad Masad

We're excited to launch this new part of our site.


A Swift REPL

Tue Jun 14 2016 by Amjad Masad

In this age of containers it's much easier to run arbitrary code in the cloud. The harder parts are scaling the service, making it reliable, and —as in this case— creating cool and useful experiences. When we looked at existing Swift REPL implementations on the web we found that none delivered a stateful and interactive environment. Just an editor with a run button.