At a software architecture conference last year, one of the speakers, a performance engineer, was talking about great application UX. He went off on a tangent at the start of his talk and said:

"Slack is what IRC should have been."

As a result of Slack's burgeoning popularity and mainstream prominence (I've seen ads for Slack pasted on my local light rail), we've seen a bunch of developer topic-focused, public Slack groups popping up over the last few years. They look and operate a lot like the IRC topic channels we've had for years, but with more usability and a lower barrier to entry.

While there are a lot of stinkers out there, I've also found many truly awesome Slack communities in the last couple of weeks. I'd like to share a semi-exhaustive, categorized list, along with my notes on the quality of each in terms of relevance, responsiveness, and activity/flow.

My simple rating system

For each of the groups, I submitted a request to join and took a look at the activity levels of the main channels. I have three subjective ratings:

Relevance

Flow

Responsiveness

I gave a rating of low relevance if more than 50 percent of the discussion looked unrelated to the topic of the group. Even some poor-quality groups had high relevance because, despite low levels of interaction, it was all on topic. I gave extremely high relevance ratings to groups that have a large amount of helpful subtopic channels with significant levels of activity.

Flow ratings were based on an average of around 30 messages a day. If the group's main channels consistently had over 30 messages, I gave them a high flow rating. Below that number, I gave a low flow rating. Obviously, a low flow rating isn't a bad thing. Less noise means more signal, right?

For responsiveness, I gave a rating of responsive if it only took an hour or two for people in the main channels with questions to get a response from someone else in the community. I checked for several instances of questions and then time-to-response in each group, so I confirmed trends of responsiveness or unresponsiveness. I didn't count it against a group if no one responded quickly to 4:00 am questions (Eastern time). It was pretty obvious when a group was unresponsive.

As for the number at the end of each group's ratings, that's the number of members in the largest channel rounded down to the nearest hundred or tenth. The numbers are always changing, so I just simplified things.

What I didn't include

All of these Slack groups are free to join. I didn't include any that charge a fee. The only ones I found that did charge a fee were either location-specific groups or remote working groups. I also didn't include any location-specific groups, because those wouldn't be relevant to most of the readers of this article. If you're interested in joining one, try searching your location + "slack group" to see what you find. There might be a great one for your area.

I didn't find any good groups for some major topics such as Java, C#/.NET, AWS, software architecture, and databases (MySQL, Oracle, or Microsoft SQL). If you know of any, please send me a link in the comments. You'll find a few of these topics in my list, but they aren't very good. So why did I include them? For some topics such as Go, I had already found an excellent group, so if I found others that weren't very good, I removed them from the list. But topics such as Java, Scala, and Microsoft devs didn't have any better alternatives, so I put them in the list, and you can see that their poor ratings reflect their quality.

Hopefully, this list will help you find a group that's extremely beneficial for your day-to-day development work and research. If you find a group that's about a topic you're interested in but it's not very high quality, then maybe you should try to improve that group or build your own. That's my goal for this article: to encourage you to make something!

Programming languages

Java Specialists — Relevance: High / Flow: High / Responsive — 3,400+

A Slack group for Java developers from the organizer of the JCrete conference.

Babel.js — Relevance: High / Flow: High / Responsive — 2,300+

A general discussion and support forum for Babel.js users. Babel.js is a ECMAScript 6-to-ECMAScript 5 compiler that lets you write ES6 features into your JavaScript code, even if some features aren't supported yet by browsers.

Clojurians — Relevance: High / Flow: High / Responsive — 5,600+

The official clojure.org Slack group. Covers the Clojure programming language and Clojurescript.

Erlang — Relevance: High / Flow: Low / Responsive — 700+

A Slack group for discussing the Erlang programming language. Includes general and learning channels.

Functional Programming — Relevance: High / Flow: Medium / Responsive — 2,400+

A discussion forum for research, questions, tools, and other topics around functional programming.

Gophers — Relevance: Extremely High / Flow: High / Responsive — 6,200+

A community of Go programming language (Golang) developers. It features channels for beginners, jobs, code review, DevOps, CoreOS, and Docker.

Microsoft Developer Chat — Relevance: Low / Flow: Very low / Unresponsive — 100+

A Slack group for ASP.NET, C#, F#, .NET, Visual Basic, and other Microsoft technology developers.

Node.js — Relevance: High / Flow: Low (very low for non-dev channels) / Responsive — 1,300+

A Node.js and JavaScript development community. The dev channel is the only relatively active channel.

Python Developers — Relevance: High / Flow: Low / Responsive — 1,000+

A community for Python developers. Includes a specific channel for getting help with issues.

Ruby Developers — Relevance: High / Flow: Very low / Unresponsive — 1,500+

A forum for developers using the Ruby language. It has channels for beginners, code, DevOps, and Ruby on Rails.

Scala Chat — Relevance: Low / Flow: Very low / Unresponsive — 400+

A Slack group for discussing the Scala programming language.

Swift-lang — Relevance: High / Flow: Medium / Responsive — 1,400+

A community for Swift programmers. Most of the relevant discussions happen in the general channel, despite 19 topic channels.

Typescriptpdx — Relevance: High / Flow: Low / Responsive — 60+

A forum for discussing TypeScript questions.

Learning programming

WeLearnJS — Relevance: High / Flow: Very low / Unresponsive — 400+

A Slack group for learning JavaScript, with several channel categories.

General coding

#devchat — Relevance: High / Flow: Very low / Responsive — 1,600+

A Slack group for asking development questions. There are 53 channels covering the major languages, various libraries and frameworks, beginner questions, and a number of other topics such as testing, machine learning, and DevOps. It has a 10K-message limit.

Scotch.io — Relevance: Medium / Flow: Low / Slow responses — 2,900+

A Slack chat based around the community web development tutorial site Scotch.io. Has different channels for CSS, PHP, Node.js, JavaScript, and Ruby.

Spec Network — Relevance: Medium / Flow: Low / Responsive — 4,400+

A Slack community for developers and designers. Built around the spec.fm podcast community, the Slack group includes 22 channels for team-ups, design, tools, jobs, events, and other general industry topics.

Technology Masters — Relevance: High / Flow: High / Responsive — 800+

A community with active channels covering the software industry from business, technology, and programming angles.

Mobile

Android United — Relevance: Extremely high / Flow: Low (per room) / Responsive — 1,000+

A discussion forum for Android developers, with 22 channels on various subtopics, including NDK, tools, architecture, libraries, testing, hiring, Android wear, and more.

Ionic Worldwide — Relevance: High / Flow: High / Responsive — 6,000+

A Slack group for developers using the Ionic framework, a tool for building hybrid mobile web apps. Includes channels for technical questions and design opinions.

Testing

#Testing — Relevance: Low / Flow: Low / Responsive — 900+

A Slack chat for quality assurance and testing discussion (manual QA, automated testing, and all other forms of software/hardware testing).

JavaScript web frameworks

Angular Buddies — Relevance: Extremely High / Flow: High / Responsive — 3,900+

A community of AngularJS (1 & 2) developers. It has 93 channels, including Angular 2.0, beginners, jobs, Angular-bootstrap, Angular Material, code reviews, and testing Angular apps with Selenium WebDriver.

Angular Chat — Relevance: Medium / Flow: Very low / Unresponsive — 1,500+

A chatroom for discussing AngularJS. There are channels for Angular 2, modules, testing, and questions.

Ember.js Community — Relevance: High / Flow: High (in main channels) / Responsive — 4,500+

A community forum for users of the Ember.js JavaScript framework. It has 87 channels.

The Meteor Chef — Relevance: High / Flow: High / Responsive — 1,900+

A forum for questions and content about the Meteor platform.

Reactiflux (on Discord, not Slack) — Relevance: Extremely high / Flow: High / Responsive — 7,000+

A community for React and React Native developers. Has many channels covering key React libraries and other projects often used in conjunction with React. There is also a room for help questions, code review, and jobs.

Socket.io — Relevance: High / Flow: Low / Responsive — 10,800+

A Slack room for discussing Socket.io, a JavaScript tool for real-time socket communication. The room has 96 channels, including several related topics such as Node.js, JavaScript, and AngularJS. The general channel has the most traffic.

Python web frameworks

Django Developers — Relevance: High / Flow: Very low / Slow responses — 300+

A forum for developers using the Python-based web framework, Django. It has channels for libraries and help questions.

Ruby web frameworks

Full Slackers — Relevance: High / Flow: Low / Responsive — 500+

A Slack community mainly focused on answering questions for Ruby on Rails beginners in the stackoverflow channel.

Ruby on Rails Link — Relevance: Extremely high / Flow: High / Responsive — 2,100+

A Slack community for Ruby on Rails developers. It has 17 channels, including a beginners and mentors chat.

PHP web frameworks

LaraChat — Relevance: Extremely high / Flow: High / Responsive — 9,200+

A community of PHP developers who use the Laravel web framework. Channels include API, internals, Laravel 4, Laravel 5, questions, testing, and tools. Still has a 10K-message limit.

Symfony2 — Relevance: High / Flow: Low / Responsive — 200+

A community of PHP developers who use the Symfony2 web framework. Most traffic is in the questions channel.

Java/Groovy web frameworks

Grails Community — Relevance: High / Flow: High (in questions) / Responsive — 1,700+

A Slack room for general discussion and questions about using the Grails framework for the Groovy programming language.

Databases

MySQL Community — Relevance: High / Flow: Very low / Unresponsive — 70+

A Slack group for developers and DBAs using MySQL. The main channel is the help channel.

Ops / Production

DevOps Chat — Relevance: Extremely High / Flow: High / Responsive — 2,100+

A forum for DevOps professionals and developers whose 23 channels cover topics such as AWS, config management, Chef, ChatOps, Docker, Puppet, security, jobs, and monitoring.

Kubernetes — Relevance: High / Flow: High / Responsive — 4,200+

A Slack group for questions and general discussion about Kubernetes, a container cluster management tool. Includes a novice channel.

ITCrowd — Relevance: Low / Flow: Low / Unresponsive — 100+

A forum for IT support workers to talk about their issues and sysadmin trends.

Rest Azured — Relevance: High / Flow: Low / Responsive — 80+

A community of Azure cloud services users. Mainly questions about user support, documentation, and deeper technical aspects of Azure.

Data science / machine learning / big data

Open Data Community — Relevance: Extremely High / Flow: Low / Responsive — 1,300+

A Slack community for sharing, discovering, and discussing publicly available data sets. Ten channels cover fields such as geospatial data, health data, and other scientific data. A good one for the software engineering data scientist.

Security

OWASP — Relevance: High / Flow: Low / Responsive — 500+

A forum for security topic discussions and the OWASP community. Channels include learning, ask OWASP, cheatsheets, developers, appsec, bug bounties, and appsec USA (the conference). There are 96 channels total.

Miscellaneous

APIs You Won't Hate — Relevance: High / Flow: Low / Responsive — 800+

A Slack chat with help, tooling, and general discussion channels around REST and APIs.

Game Development — Relevance: Extremely High / Flow: High / Responsive — 2,100+

A community of game developers that has 69 channels, including level design, programming, Unity engine, marketing, and testing.

Ghost — Relevance: High / Flow: Medium / Responsive — 4,700+

A forum for users and developers of the Node.js-based blogging platform, Ghost.

IoT Geeks — Relevance: Low / Flow: Low / Unresponsive — 500+

A chatroom for discussing high-level thoughts about the Internet of Things and smart homes.

Making Wordpress — Relevance: High / Flow: High / Responsive — 9,600+

A Slack group for the Wordpress open-source committers and the general community, but most of the discussion is around developing the platform, not building Wordpress sites. It has 62 channels, including forums for theme review, core development and API, events, training, and accessibility.

tvOS Developers — Relevance: Low / Flow: Low / Slow responses — 100+

A community for developers who make apps for the Apple TV via tvOS.

Regional Slack channels

Check out this github page that includes a large number of regional Slack channels organized by city or country.

Are there any other developer-oriented Slack groups I didn't find? This list is constantly evolving, so please suggest any additions in the comments if they have high relevance and responsive community members.

Keep learning