Signal

Signal's Terms of Service state plainly: "Signal is based in the United States. Signal transfers encrypted information and metadata to the United States and other countries where it has or uses facilities, service providers, or partners." Disputes must be resolved in the US District Court for the Northern District of California or a California state court. The Signal Technology Foundation is incorporated in Delaware and headquartered in Mountain View, California. Signal's infrastructure runs on AWS, Google Compute Engine, and Microsoft Azure worldwide, with no public confirmation of EU-specific hosting. Signal's GDPR compliance page is sometimes cited as evidence of EU server location, but that page describes contractual safeguards (Standard Contractual Clauses) for transferring EU users' data to the US, which is the opposite of EU-based hosting. This is a US-jurisdiction service, which is why this question scores 0 despite Signal's exceptional privacy architecture (scored separately in 1.2–1.4).

Signal uses the Signal Protocol (Double Ratchet + X3DH) for full end-to-end encryption by default on all messages, voice, and video calls with no option to disable it. In 2023, Signal added PQXDH, a post-quantum extension to key exchange. In 2025, it introduced the Triple Ratchet, which combines classical and post-quantum ratchets. Because content is E2EE, Signal's US jurisdiction (see 1.1) does not expose readable messages. The company itself cannot decrypt messages, even under legal compulsion.

Signal's business model is donations; it has no advertising and no data brokering. Its privacy policy states it collects only the minimum necessary data: phone number at registration and a coarse last-connection date. Since February 2024, phone numbers are no longer shown to other users by default. They can be replaced entirely with an optional username for contact. This is a concrete reduction in the personal data Signal users see about each other, beyond what the servers ever held.

Signal does not use message content or metadata for AI training because content is E2EE and unreadable to the service. In April 2026, President Meredith Whittaker confirmed at the FIBE-2026 conference in Berlin that Signal will not integrate AI features or chatbots. She framed this as a direct consequence of its non-profit, donation-only funding model, which removes any incentive to monetize data via AI.

All Signal components — Signal-iOS, Signal-Android, Signal-Desktop, Signal-Server, and the libsignal protocol library — are published on GitHub under AGPLv3, an OSI-approved copyleft license. The server's anti-spam component is a documented exception and remains closed-source to prevent abuse, but the core product is bona fide open-source.

Signal's cryptographic design has strong historical grounding through Trail of Bits and Cure53 engagements and formal academic verification of the Signal Protocol (IEEE, 2017). However, no formal, commissioned third-party audit with a published report covering the current codebase was confirmed in the last three years. The closest recent scrutiny is an independent, uncommissioned eight-part cryptographic review published by security researcher Soatok in 2025. It found no exploitable attacks but is informal analysis, not a paid audit with a scoped public report. Two desktop CVEs (CVE-2023-24068 / 24069) were disclosed and fixed in 2023. This mix of strong historical work and no recent formal audit report deserves partial, not full or zero, credit.

Signal's repositories have contribution guidelines and issue tracking on GitHub. The Signal Technology Foundation is a 501(c)(3) with a named board (including Meredith Whittaker and Brian Acton), and its governance and finances are disclosed in annual filings.

Signal is entirely free with no subscription, purchase, or paywalled tier. President Meredith Whittaker stated operating costs run in the tens of millions per year, covered entirely by voluntary donations, with no cost passed to users.

There is only one tier. Messaging, voice and video calls, groups, Stories, disappearing messages, and as of April 2026, cross-platform local backups are all available to every user at no cost, with no premium tier.

There is no pricing to obscure: no checkout, upsell, or upgrade prompts. Donating is optional and carries no feature unlock or restriction.

Signal has no price at all — not even a paid tier for extra storage or features, unlike freemium services. This question is therefore excluded from the Pricing Model total, reducing that section's maximum from 17 to 14 points, per the N/A rule for products with no price whatsoever.

Signal's on-device data is readable by the open-source clients, and Android users can move data between devices via chat backups, but there is still no built-in export to a portable, open, structured format for all platforms. As of April 2026, Signal shipped cross-platform local backups (Android, iOS, and Desktop), improving data transfer between devices. However, Signal Desktop's plaintext/JSON chat export, discussed since early 2025, remained forthcoming rather than a shipped, stable feature as of this review. Third-party community tools (e.g. signalbackup-tools) can parse the proprietary backup format into plain text, but that is not an Apple- or Signal-provided export path.

Signal does not support self-hosting. Signal-Server is published under AGPLv3, but Signal provides no deployment documentation for running an independent server. A self-hosted instance cannot interoperate with the main Signal network because the project is architecturally centralized around Signal's own infrastructure.

Messages are cached locally and remain readable offline once received. However, sending or receiving new messages requires connectivity because core communication depends on the network.

Signal ships official clients for iOS, Android, Windows, macOS, and Linux (including .deb packages for Debian/Ubuntu), with the Android APK also available for direct sideloading outside the Play Store. Linux is a genuinely open, non-proprietary platform with an officially maintained client.

Signal supports standard OS accessibility layers — VoiceOver on iOS, TalkBack on Android, basic keyboard navigation on desktop — but publishes no dedicated accessibility policy, WCAG conformance statement, or systematic accessibility commitment.

Signal Messenger LLC is wholly owned by the Signal Technology Foundation, a US 501(c)(3) non-profit incorporated in Delaware. There are no venture-capital investors; Brian Acton's founding $50M was structured as a loan to the non-profit, not an equity stake.

The Signal Technology Foundation has owned Signal Messenger LLC continuously with no acquisition or investor change. Leadership transitions, such as Moxie Marlinspike stepping down as CEO in January 2022 and Meredith Whittaker becoming president in September 2022, are internal governance changes, not ownership transfers. As of June 2026, Whittaker continues to serve as president and makes public appearances defending encryption to UK officials.

Signal has an unusually assertive public ethics record: no advertising ever, explicit refusal to add AI features in April 2026 tied directly to its non-profit mission, and sustained advocacy against encryption backdoors. Signal threatened to withdraw from the UK in 2023 over the Online Safety Bill's client-side scanning provisions. In June 2026, the Foundation published a statement, "Surveillance Is Not Safety," opposing renewed UK proposals for phone and content scanning under the Online Safety Act. Whittaker stated Signal would "absolutely, 100% walk" from the UK rather than weaken encryption. Signal has taken the same position against the EU's Chat Control proposals, saying it would leave the EU market before implementing client-side scanning.

Signal has not published a sustainability report, green-hosting commitment, or any information about the energy sourcing or carbon footprint of the AWS, Google, or Azure infrastructure it uses. This is a genuine gap given the Foundation's transparency in nearly every other area.

Signal, which unified TextSecure and RedPhone, launched in July 2014. It has had 12 years of continuous active development as of this review, growing from a niche tool to a mainstream app used by hundreds of millions.

Signal maintains over 126 public GitHub repositories with frequent commits, an active community forum (community.signalusers.org), and a large presence on Reddit (r/signal). Releases ship across platforms multiple times per month. The team publicly shares roadmap items and yearly feature recaps via its blog.