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Mattermost

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Panel rating · 6 judges · How to read the stars

Category median

Sovereignty: 1 of 4 dimensions proven

0–5 in half steps. 5 means the rubric's top anchor is met on the evidence.

by Mattermost, Inc. · mattermost.com

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Read this page as one judge. Each weighs the same scores by what they care about.

The Works Council Advocate

Weighted verdict

Knows that a chat log is a record of who spoke to whom at what hour. Wants presence a person controls, no individual activity scoring anywhere, retention that deletes rather than hides, and analytics that can be switched off across the organisation.

Same scores as the panel view — this lens weights them the way this judge cares.

Scored by The Works Council Advocate

Channels, threads & search

How this is scored

The daily surface: channel model, threading, mentions, files, and whether search can find a decision made eighteen months ago.

0 — Flat group chats with no threads; search covers recent messages only, and history is capped.

3 — Channels and direct messages with basic search, but threading is awkward or absent and file handling is a plain attachment list.

5 — Public and private channels, real threads, mentions and reactions, file sharing with previews, and full-text search across the whole history.

8 — Cross-organisation or guest channels with clear boundaries, message editing history, pinned and saved items, search with filters by channel, person and date, and a documented history limit or none at all.

10 — The archive is a working knowledge base: search that ranks well across years, threads that stay readable, channel lifecycle management (archive, rename, merge) without losing history, and export of a conversation in a form a human can read.

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The Works Council Advocate

Channels and threads are real enough to have their own API endpoints and even a beta operation to move a thread to another channel, with guest accounts, file previews, and, on the Enterprise plan, shared channels and Matrix-protocol federation; edits and deletions are retained in the record by default, and search is documented at a three-million-post scale on Professional and beyond that on Enterprise. We found no public information on pinned or saved items, search filters by channel, person or date, or channel archiving and merging. 2 5 6 9 10

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Encryption & access control

How this is scored

What is encrypted and against whom, plus who can reach which room. Judged on documented mechanism, since "encrypted" in this category usually means the vendor holds the keys.

0 — Transport encryption only, undocumented; no role model beyond admin, guests indistinguishable from members.

3 — TLS and encryption at rest with vendor-held keys, basic roles, and guest access that mostly works.

5 — The above plus configurable roles per channel, SSO, guest accounts with scoped visibility, and a clear statement of what the vendor can read.

8 — Optional end-to-end encryption for direct messages or private rooms with the trade-offs named, device verification, session management an admin can revoke, and documented key handling.

10 — End-to-end encryption as a first-class mode — documented or open cryptography, cross-device key management that ordinary users survive, identity verification, and the vendor stating plainly what it cannot decrypt.

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The Works Council Advocate

Transport and at-rest mechanisms are documented concretely — TLS with AES-256 and 2048-bit RSA, disk-level encryption on infrastructure the customer runs, S3 with S3-managed keys, and cluster traffic encrypted with AES-256 — and the deployment guide says plainly that the database is not encrypted at the application layer so that search and compliance reporting keep working, which is the kind of honesty I want more of. Granular role-based access, AD/LDAP sync, SSO, guest accounts and zero-trust channel access are evidenced; we found no public information on end-to-end encryption of message content, device verification, or sessions an administrator can revoke. 2 4 7 8

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Retention, discovery & co-determination

How this is scored

The archive as a legal object: retention policies, export for discovery, audit, and the monitoring features a works council will ask to have switched off.

0 — No retention policy, no export beyond a manual copy, no audit log, and presence or activity analytics that cannot be disabled.

3 — Manual export of some data and a global history limit, but no per-channel retention, no audit log and no admin control over analytics.

5 — Configurable retention per channel or workspace, admin export in a documented format, an audit log of administrative actions, and status or presence that a user can control.

8 — Legal-hold and eDiscovery export including edits and deletions, retention executed per policy and evidenced, full admin audit trail, and activity analytics switchable off organisation-wide.

10 — Built to pass a works agreement and a subpoena on the same day: granular retention with documented deletion, discovery export a lawyer can use, complete audit, and no individual-level productivity scoring anywhere in the product.

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The Works Council Advocate

Compliance export runs in formats a lawyer already uses — Global Relay EML, Actiance XML, Proofpoint — tracking each message by ID through edits and deletions, with job status visible and every query and download action logged in an audit history explicitly to prevent unauthorised queries; that last part is the co-determination instinct done right. Data Retention Policy and Legal Hold are named at the Enterprise tier and self-hosted telemetry can be opted out; but the default retains everything including deletions rather than deleting, and we found no public information on presence a person can control or on activity analytics and whether they can be switched off organisation-wide. 2 4 9 10

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Deployment & data custody

How this is scored

Whether the customer can hold their own archive: self-hosting, private cloud, open source, federation, and what an exit actually looks like.

0 — Cloud-only, proprietary, with export limited to a partial archive.

3 — Cloud-only, but with a documented full export in an open-ish format.

5 — A private-cloud or dedicated-instance option, or a self-hosted edition that lags the cloud significantly; full export documented.

8 — A genuine self-hosted edition close to feature parity, or open-source core with a documented upgrade path, plus complete export including files and metadata.

10 — Custody is the customer's: open-source or source-available server, self-hosting supported as a first-class deployment, open protocol or federation, and a migration path in and out that the vendor documents rather than resists.

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The Works Council Advocate

Custody really can be the customer's: the same server installs via Kubernetes, Linux or containers, an air-gapped runbook with a bill of materials and registry mirroring is published, FIPS-compliant STIG-hardened images exist, and the customer stands up the database, file storage and TLS themselves — with Matrix-protocol federation and Slack-compatible webhooks giving paths in and past message history exportable via a command-line tool. The compliance export excludes Playbooks and Boards data, and we found no public information on a complete single-format export of an entire workspace. 2 9 11 12

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Integrations & extensibility

How this is scored

Bots, webhooks, app framework, identity — whether the chat becomes the place work is noticed, and whether that is buildable without a partner agreement.

0 — No API, no webhooks, no bots.

3 — Incoming webhooks and a handful of native integrations; no bot framework, no documented limits.

5 — Documented REST API, incoming and outgoing webhooks, slash commands, a bot account model, and SSO.

8 — A proper app framework with interactive components, event subscriptions with retries, SCIM provisioning, documented rate limits and a sandbox.

10 — A platform: versioned API with a deprecation policy, an app directory or plugin system with permissions a customer can audit, and integrations the vendor maintains rather than lists.

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The Works Council Advocate

A versioned REST API documented endpoint by endpoint with its permission requirements, incoming and outgoing webhooks available on every plan including the entry edition, Slack-compatible webhook payloads, interactive dialogs and Mattermost Blocks, plus admin-enforced channel locking for webhooks — a control I am glad to see. We found no public information on an app directory, SCIM provisioning, documented rate limits, or an event-subscription model with retries. 2 5 6 13 14

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European sovereignty

How this is scored

Where the archive and its metadata live, who the contracting entity is, which subprocessors touch it. Independently sourced by the sovereignty pipeline; scored here as this buyer weighs it.

0 — Non-EU vendor and contracting entity, hosting unstated or non-EU, subprocessors unnamed.

3 — EU data residency offered for message content while metadata, search indexes or support tooling remain non-EU, or the contracting entity sits outside the EU.

5 — EU hosting as standard and an EU contracting entity, but parts of the chain — notifications, AI features, analytics — are non-EU without an explained safeguard.

8 — EU hosting on named infrastructure, EU contracting entity, full subprocessor list published, any non-EU processing named with its legal basis.

10 — Sovereign end to end and evidenced: vendor, entity, hosting and every subprocessor European, certification published, and a self-hosted option that removes the question.

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The Works Council Advocate

The captured pages show a United States vendor relying on the EU–U.S. Data Privacy Framework and Standard Contractual Clauses, personal information transferred to the United States, Google Analytics on the sites, Azure and AWS named as cloud hosting for US-headquartered providers, and no published list of the subprocessors behind the vendor-managed cloud. The documented air-gapped, self-hosted path with telemetry opt-out is what removes the question in practice for a European deployment, but the contracting entity sits outside the EU and we found no public information on EU hosting or an EU entity. 3 4 12

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Pricing transparency not rated — the vendor publishes no price

How this is scored

Whether a buyer can compute the annual invoice for their headcount — including the retention, compliance and guest features they actually need — from public pages alone.

0 — No public prices at all; every tier is a sales conversation.

3 — A per-user headline exists, but the tier where retention control, SSO or compliance export begins is unstated.

5 — Per-user prices public with billing period stated, but at least one commonly needed capability (unlimited history, SSO, eDiscovery) sits in an unpriced enterprise tier.

8 — Every tier priced publicly with per-user maths, history and storage limits, feature boundaries, minimum term and VAT treatment stated; self-hosted licensing priced too where offered.

10 — Complete price computability: annual invoice derivable for a given headcount and deployment choice, including guest users, storage and any per-instance licence.

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The Works Council Advocate

The captured pricing page routes every named plan to a sales conversation — Professional to "Contact Sales", Enterprise to "Get Pricing", Enterprise Advanced to "Request Quote" — and we found no public per-user price for any tier anywhere in the captures. A limited-use free edition of Enterprise Advanced is offered for technical evaluation, but no buyer can compute an annual invoice from these pages. 2

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European sovereignty — proven facts

1 of 4 dimensions proven

Built only from facts shown on the vendor's own pages. A dimension we could not prove is left open, not scored as zero.

Ownership Not determined — uncited Report an error
Data residency Not determined — uncited Report an error
Subprocessors US CLOUD Act reach ⚠ unverified 0/2 pts 3 Report an error

Where this could be wrong

What we left out

A claim that does not survive our checks costs us the claim, not the page. This is what was taken off this one.

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Sources (14)

The pages every claim on this page was read from — each one checked, dated, and kept verifiable.

  1. 1 Vendor homepage mattermost.com Checked 15 Sep 2026 Details →
  2. 2 Pricing mattermost.com Checked 15 Sep 2026 Details →
  3. 3 Security page mattermost.com Checked 15 Sep 2026 Details →
  4. 4 Privacy policy mattermost.com Checked 15 Sep 2026 Details →
  5. 5 Channels, threads & search — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  6. 6 Channels, threads & search — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  7. 7 Encryption & access control — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  8. 8 Encryption & access control — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  9. 9 Retention, discovery & co-determination — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  10. 10 Retention, discovery & co-determination — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  11. 11 Deployment & data custody — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  12. 12 Deployment & data custody — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  13. 13 Integrations & extensibility — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  14. 14 Integrations & extensibility — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →