Rocket.Chat vs Slack
When comparing Rocket.Chat vs Slack, the Slant community recommends Rocket.Chat for most people. In the question“What is the best chat software?” Rocket.Chat is ranked 6th while Slack is ranked 12th. The most important reason people chose Rocket.Chat is:
Rocket.Chat is available for free. It's licensed under the MIT license with source code available on [GitHub](https://github.com/RocketChat/Rocket.Chat).
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free and open source
Rocket.Chat is available for free. It's licensed under the MIT license with source code available on GitHub.
Pro Native apps for all major desktop and mobile platforms
Rocket.Chat has native apps for macOS, Windows, Linux, iOS and Android.
Pro Supports a wide variety of authentication methods
In addition to the usual email / username + password combination, Rocket.Chat supports authenticating via Facebook, Github, Gitlab, Google, Linkedin, Meteor and Twitter accounts.
Pro Understands markdown better than Slack does.
Links work properly, for instance, with square brackets followed by parentheses.
Pro Very active and helpful community
Pro Video conferencing support
Rocket.Chat supports video calls.
Pro Drag & drop files in channels
You can upload a file to any channel over HTTPS simply by dragging and dropping.
Pro Fantastic search functionality
You can deep search messages, files and snippets. Given Slacks integration into many external services, Slack is good enough to act as the central search interface for your entire team.
Pro @mentions
You can ping people to get their attention even if they are not online by @mentioning them. Slack supports desktop notifications.
Pro Very polished user experience
The entire Slack interface is polished and intuitive to use. There are very few bugs or inconsistencies in the UI and it's very fast to use. There is nothing in particular that is new with Slacks implementation of team chat, but the execution of the groups (called channels), search, external service integration and notifications is close to perfect.
Pro Apps for iOS, Android, Windows Phone, Mac OS, Linux, and Windows
Slack has apps for iOS, Android, Windows Phone, Mac OS, Linux, and Windows to give you the full functionality of Slack with some extra features not found on the website on most major platforms.
Pro Supports multiple teams
You can be signed into multiple teams simultaneously and quickly switch between them.
Pro Freemium plan
Free forever, only restriction on searchable message archives, up to 10k of your team’s most recent messages and 10 apps or service integration. Great for trying out first.
Pro Robust integration with a huge number of tools
Slack integrates with tools like Trello, GitHub, Dropbox, Mailchimp, and dozens of others, so you can have a centralized event feed of your project right alongside your chat. This is tremendously useful for keeping context with your discussions.
Pro Emoji reactions to limit excessive posts and notifications
Pro Multiple channels for different groups
Pro Syntax coloring
Pasted code can be colored based on syntax.
Pro Edit messages easily
It allows you to change what you sent by hovering to the message and selecting "Edit message" under the ellipsis (...).
Pro GIFS
easily embed gifs with /giphy
slash command.
Pro IRC connectivity over SSL
Pro Flexible, granular notification settings
Notifications are handled separately for mobile and the web app. You can receive notifications for all messages, just direct messages, or based on filters, and you can have different settings for different channels: you don't have to get notified every time someone pushed to GitHub or every time someone posts to off-topic chat, unless you want to.
Pro Inline link previews (photos, mockups, etc.)
When a link is added, some content in the link is shown such as image - like how Facebook does it when you share a link.
Pro Slackbot extensible chat robot
The "Slackbot" can is an extensible robot that can be set you remind you about tasks, auto respond to certain phrases and a variety of other functionality.
Pro Dev team is invested, responsive, and friendly
Having submitted both feedback and support requests for bot development, I can personally attest that the team takes feedback seriously, and responds quickly to communication. This is vital for any closed-source or hosted project.
Pro Shows local time of each participant
You can click on the profile of a user to see their local time. An especially useful feature when members of your team are working in different timezones.
Pro Self chatting
Creative implementation which is very good for personal journaling or drafting/collecting ideas. Previously, to do this, users needed to create a private channel with themselves. Note that some other team-chat apps may disallow creating group/channel with no 2nd person(s).
Pro Can Create Diagrams with Creately
You can just create flowcharts, org chart, mind maps, UML charts, infographics and many more by typing /creately new <document name>
Pro It can surprise you
There's a checkbox in preferences under advanced options that may surprise you.
Cons
Con Developer support is non-existent
Can't even create a clean Ubuntu VM with a working developer install. Unresolved dependencies; fails to build. Docs are terrible; actual devs don't respond to questions; error messages are near-opaque. DO NOT RECOMMEND.
Con Web client loses images
In chat rooms with images, before very long, images start to become empty boxes. Useless to pass around visual information
Con No theme customization
Con No chat audit for enterprise
Con Poor security implementations / protocols
Con Centralized
Con iOS app is poorly made
The iOS application is not native, being just a browser container. This means that the UX is quite poor, slow, buttons unresponsive. At this moment they do not provide a decent experience.
Con Android app is poorly made
The Android application is just a badly wrapped web-view which does not perform well and has no form of offline caching whatsoever.
Con Privacy settings are absent
Privacy settings for the server are absent, for instance, you don't have the ability to disable registrations, there's no way to control access to the chat.
Con Features not available out of the box
Con No web browser support
Con Email required for registration
Con No way to block new registrations
Without the ability to disable registrations, there's no way to control access to the chat.
Con "Native" desktop apps are web apps
While it's great that Slack provides installable apps for Windows, macOS, and Linux, they're just the Slack web app wrapped in Electron shell. This means they don't offer the same level of native UX that a truly native toolkit app would.
Con Expensive when you need to upgrade
At $6.67 per user / month (or $8 if billed monthly) , Slack is significantly more expensive than the competition if you need features such as unlimited integrations (more than 10) or unlimited message storage (more than 10,000). However, the free version of Slack includes unlimited users.
However if you need only unlimited messages you can use storage services like https://slarck.com to upload then browse and search your entire message history, while staying in Slack's free plan. So with a combo of Slack+Slarck this con is not that major.
Con No self-hosting available
If you are worried about third-parties getting access to your data you should consider self-hosting. With self-hosting you are in control over where your data is stored, who has access to it. You will also not be vulnerable to exploits of a third-party provider.
Con Hidden max limit of free users per channel
Slack says that their free accounts support an unlimited number of users, which is true. However they don't mention that there is an undisclosed maximum number of users per channel (8462). For a large open source community, this is something to keep in mind.
Con Proprietary (non-free/libre)
Con Linux client is very RAM intensive
Con Slow and lags sometimes
Con No E2E encryption
Data is sent of SSL only, not E2E encrypted.
Con API doesn't allow custom widgets in chat
Con API is overall very poor
Can't do much with integrations.
Con Awful performance and constant glitches, since it is Chromium-based
You will experience a lot of hangs and glitches and it eats immense (for as basic as UI is) amount of RAM.