Slack alternatives

Open-source alternatives

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  Mattermost Team Edition

  Fit: PartialCore overlap exists; named gaps need replacing or rebuilding.Fit is not feature parity. C Tier CDaily-workflow features need a paid edition GNU Affero General Public License v3.0 Permissions of this strongest copyleft license are conditioned on making available complete source code of licensed works and modifications, which include larger works using a licensed work, under the same license. Copyright and license notices must be preserved. Contributors provide an express grant of patent rights. When a modified version is used to provide a service over a network, the complete source code of the modified version must be made available. May Commercial useModificationDistributionPatent usePrivate use Must License and copyright noticeState changesDisclose sourceNetwork use is distributionSame license No LiabilityWarranty Summary from GitHub's choosealicense.com Apache License 2.0 A permissive license whose main conditions require preservation of copyright and license notices. Contributors provide an express grant of patent rights. Licensed works, modifications, and larger works may be distributed under different terms and without source code. May Commercial useModificationDistributionPatent usePrivate use Must License and copyright noticeState changes No Trademark useLiabilityWarranty Summary from GitHub's choosealicense.com Self-hostable: yesYou can run it on your own server.

  Team offers channels, DMs and core search, but no group calls or guest accounts. Current Slack migration guide targets Entry/paid editions; Team import parity requires verification; integrations must be rebuilt.

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  Rocket.Chat Community

  Fit: PartialCore overlap exists; named gaps need replacing or rebuilding.Fit is not feature parity. C Tier CDaily-workflow features need a paid edition MIT License A short and simple permissive license with conditions only requiring preservation of copyright and license notices. Licensed works, modifications, and larger works may be distributed under different terms and without source code. May Commercial useModificationDistributionPrivate use Must License and copyright notice No LiabilityWarranty Summary from GitHub's choosealicense.com Self-hostable: yesYou can run it on your own server.

  Slack importer handles users/channels/messages; attachments need a separate pending-file download step and existing usernames can be skipped. Community edition limits remain.

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  Element Server Suite Community

  Fit: Different approachSolves the same job differently; plan a redesign, not a copy.Fit is not feature parity. B Tier BPaid extras for admin, identity or audit GNU Affero General Public License v3.0 Permissions of this strongest copyleft license are conditioned on making available complete source code of licensed works and modifications, which include larger works using a licensed work, under the same license. Copyright and license notices must be preserved. Contributors provide an express grant of patent rights. When a modified version is used to provide a service over a network, the complete source code of the modified version must be made available. May Commercial useModificationDistributionPatent usePrivate use Must License and copyright noticeState changesDisclose sourceNetwork use is distributionSame license No LiabilityWarranty Summary from GitHub's choosealicense.com Self-hostable: yesYou can run it on your own server.

  Matrix rooms, federation and encryption differ from Slack channels and app workflows. Plan identity, integration and history transfer separately; no verified one-click importer or bridge parity claimed.

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  Zulip

  Fit: Different approachSolves the same job differently; plan a redesign, not a copy.Fit is not feature parity. A Tier ANo paid feature gates in the self-run edition Apache License 2.0 A permissive license whose main conditions require preservation of copyright and license notices. Contributors provide an express grant of patent rights. Licensed works, modifications, and larger works may be distributed under different terms and without source code. May Commercial useModificationDistributionPatent usePrivate use Must License and copyright noticeState changes No Trademark useLiabilityWarranty Summary from GitHub's choosealicense.com Self-hostable: yesYou can run it on your own server.

  Channel-plus-topic model differs from Slack threads; Slack export/import documented, private data availability depends on source export permissions.