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Free picks · Mac · Open source

Best free open-source communication apps for Mac (2026)

Every pick is listed under Communication in our directory, runs on a Mac and is free to use and tagged open source. We rank them by our rating and popularity, then favour tools made mainly for communication and apps built for Mac.

Short answer

The best free open-source communication apps for Mac are Mattermost, Zulip and Rocket.Chat, the top three of 5 matches in our directory. All 5 are tagged open source in our directory. 1 of the 5 picks is completely free and the other 4 have a free plan.

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At a glance

Counted from the top 5 picks, except the total.

Matching tools
5
Completely free
1
Open source
5
Work offline
1
Native apps
0

Comparison table

“Free plan” means a free tier with paid upgrades. A dash in Licence means our directory does not list the tool as open source.

#NamePricingPlatformsLicenceWhy pick it
1MattermostFree planWeb, Windows, macOS, Linux, iOS, AndroidOpen sourceSelf-hosted, open-source team chat with a free edition for small teams.
2ZulipFree planWeb, macOS, Windows, Linux, iOS, AndroidOpen sourceOpen-source team chat where every conversation has a topic, so threads stay readable.
3Rocket.ChatFree planWeb, Windows, macOS, Linux, iOS, AndroidOpen sourceOpen-source team chat you host yourself, free for up to 50 users.
4ElementFree planWeb, Windows, macOS, Linux, iOS, AndroidOpen sourceOpen-source, Matrix-based messaging you can self-host for free.
5HarperFreeChrome, Firefox, macOSOpen sourceA free, open-source grammar checker that runs entirely on your device.

Why each pick made the list

Every reason is taken from the tool's own listing: its categories, platforms, features, rating and pricing.

  1. Mattermost

    Free plan4.4

    Our top Mac pick, rated 4.4/5. Communication is its main purpose in our directory. Runs on a Mac, and also on Web, Windows, Linux, iOS and 1 more platform. Its listing says it is privacy-focused. On our Windows list it is number 2.

    Watch out for: You need to run and maintain your own server

    Pros, cons and detailsVisit

  2. Zulip

    Free plan4.5

    Number 2 of 5 for Mac, rated 4.5/5, the highest here. Communication is its main purpose in our directory. Runs on a Mac, and also on Web, Windows, Linux, iOS and 1 more platform. On our Windows list it is number 3.

    Watch out for: Free cloud plan only searches the latest 10,000 messages

    Pros, cons and detailsVisit

  3. Rocket.Chat

    Free plan4.2

    Number 3 of 5 for Mac, rated 4.2/5. Communication is its main purpose in our directory. Runs on a Mac, and also on Web, Windows, Linux, iOS and 1 more platform. Its listing says it is privacy-focused. On our Windows list it is number 4.

    Watch out for: Self-managed only on the free plans, so you need technical setup

    Pros, cons and detailsVisit

  4. Element

    Free plan4.3

    Number 4 of 5 for Mac, rated 4.3/5. Communication is its main purpose in our directory. Runs on a Mac, and also on Web, Windows, Linux, iOS and 1 more platform. Its listing says it is privacy-focused. On our Windows list it is number 5.

    Watch out for: Self-hosting needs technical setup

    Pros, cons and detailsVisit

  5. Harper

    Free4.5

    Number 5 of 5 for Mac, rated 4.5/5. Listed mainly under Writing, it also covers communication. Runs on a Mac, and also on Chrome and Firefox. Its listing says it works offline, is privacy-focused and is easy to pick up. It is not in the Windows top 5 (not listed for Windows).

    Watch out for: English only for now

    Pros, cons and detailsVisit

Running these on Mac

Counted from each pick's listing type and platforms.

  • By listing type, the 5 Mac picks are 4 web apps (Mattermost, Zulip, Rocket.Chat and Element) and 1 browser extension (Harper).
  • None of the 5 is listed as a native Mac app; they are web or cloud tools that are listed to run on a Mac.
  • Every Mac pick here also runs somewhere else. Element reaches furthest, on 5 other platforms besides Mac.
  • 4 of 5 also run on iPhone and iPad, so the same tool can follow you between Mac and iPhone; Harper does not.

How this list compares

The same search on other platforms, and the other price filter. Only the differences are named.

Frequently asked questions

What is the best free open-source communication app for Mac?
Mattermost is our first pick. Self-hosted, open-source team chat with a free edition for small teams. Mattermost has a free plan, with paid plans that unlock more features or usage.
Are these communication apps really free?
Yes, every pick is free to start. Harper is completely free. Mattermost, Zulip, Rocket.Chat and Element have free plans with paid upgrades.
Do these open-source communication apps work on other platforms too?
All 5 picks also run elsewhere, including Mattermost (Web, Windows and Linux), Zulip (Web, Windows and Linux) and Rocket.Chat (Web, Windows and Linux).
Which ones work offline on a Mac?
Harper is listed as working offline. The others need an internet connection for at least some features.
Which are easiest for beginners?
Harper is rated beginner-friendly. 4 picks take more time to learn.
How many free open-source communication apps for Mac are in the directory?
5 match right now, and all of them are on this page. New tools are added as they are checked.

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