Team chat with private rooms, file upload and link previews (alternative to Slack)

Question

I’ve been using Slack more and more and while I love it, the pricing is bit high for my current finances.

Basic features

• chat rooms
• private rooms
• support file upload
• link previews

Nice to have

• edition of past messages
• markdown formatting

Non important features

• desktop or mobile clients

It goes without saying that any open source solution would be perfect.

Answer 1

Miaou

Open source - runs on io.js

Basic features

• chat rooms: yes
• private rooms: yes
• support file upload: yes
• link previews: not sure

Nice to have

• edition of past messages: yes
• markdown formatting: yes

Non important features

• desktop or mobile clients: web based only

Installation's slightly tricky since its currently in development, but it works great with ubuntu 14.04 lts and the nodesource io.js repos. I'm currently doing an install guide for it. However its possible for someone with an intermediate level of skill to install (though, I got a bit of help from the developer) it from scratch in an afternoon. Installation is also possible via Vagrant or Docker.

Live demo, actually used by several communities: https://dystroy.org/miaou

Answer 2

Rocket.Chat

Open Source, Meteor alternative.

Existing Features

• Free Open Source Software
• Hassle free MIT license
• BYOS (bring your own server)
• Multiple Rooms
• Direct Messages
• Private Groups
• Public Channels
• Desktop Notifications
• Edit and Delete Sent Messages
• Mentions
• Avatars
• Markdown
• Emojis
• Transcripts / History
• File Upload / Sharing
• Unlimited Archive
• I18n - [Internationalization with Lingohub]
• Hubot Friendly - [Hubot Integration Project]
• Media Embeds
• Link Previews
• LDAP Authentication
• Face to Face Video Conferencing aka WebRTC
• REST-full APIs
• Remote Locations Video Monitoring
• Native Cross-Platform Desktop Application
• Native iOS Application
• Native Android Application

In Progress

• External popout window for chat with website visitor (like Zopim, Olark, LiveChat, SnapEngage)

Planned

• Off-the-Record (OTR) Messaging
• Full text search
• Kerberos Authentication
• XMPP Multi-user chat (MUC)

Disclaimer

I am from the dev team of this project.

Answer 3

Let's chat

• open source
• no markdown support. But it may come sooner or later
• no editing of previous messages. Yet
• link preview/image embed. More on this
• Using XMMP

Answer 4

Kaiwa

• open source
• edition of sent messages
• no markdown support. But it may come sooner or later
• linking preview via oEmbed
• Using XMMP

Answer 5

Matrix

(Pictured: Vector, one of many Matrix clients)

Open, federated protocol with many server and client implementations.

• chat rooms + private chat rooms
• file uploads

• link previews: depends on the client

• edition of messages: in the works

• markdown formatting: depends on the client
• multiple desktop and mobile clients
• open-source

Answer 6

Gitter.im

• needs a gihub account
• support markdown
• past messages can be edited before a certain delay
• clients for desktop and phones (iOS, Android)
• paid application with a free plan

Answer 7

Mattermost

• No limits on searching archive (vs. Slack requires subscription after 10,000 messages)
• Editing of past messages
• No markdown support. Yet
• Link preview (Youtube, etc)
• File upload
• Web only (albeit responsive for touch devices)
• Private chat rooms: Yes
• Open Source

You may submit feature request using uservoice

Answer 8

HipChat

Not open source. Acquired by Atlassian a few years ago. XMPP based.

Basic features

• chat rooms: yes
• private rooms: yes
• support file upload: yes
• link previews: yes
• hosted or on-premise: both available

Nice to have

• edition of past messages: not yet
• markdown formatting: not yet (although there is a Chrome extension for the web client)

Non important features

• search archive: 25,000 messages on free plan (vs. Slack requires subscription after 10,000 messages)
• desktop or mobile clients: both