1. Privacy and encrypted communication
Signal is designed to provide private messaging and internet calling with end-to-end encryption. Signal states that message and call content cannot be decrypted or accessed by the service because communication is encrypted between the people participating in the conversation.
Signal also states that it does not sell, rent, or monetize personal data or communication content. Its privacy model is built on limiting the amount of information required to operate the service while keeping private communication content outside the service’s readable data.
2. Account information
A phone number is required when registering a Signal account. Signal uses that number to provide account and communication services. Users may also add profile information such as a profile name and profile picture.
Signal describes profile information as end-to-end encrypted. Phone number privacy controls can also limit whether people who do not already know a user’s number can see it in profile details.
3. Messages, calls, and message history
Signal cannot decrypt the contents of messages or calls. When a recipient device is temporarily offline, Signal may queue an end-to-end encrypted message on its servers until it can be delivered.
Conversation history is generally stored on the user’s own devices rather than as readable message history on Signal’s servers. This is why account credentials such as a Signal PIN are not the same as a cloud copy of every conversation.
4. Technical information required to operate Signal
Signal stores a limited amount of technical information needed to establish calls, route messages, authenticate devices, and operate the service. Its privacy policy identifies examples such as randomly generated authentication tokens, cryptographic keys, push tokens, and other technical material necessary for communication delivery.
Signal states that this additional technical information is limited to what is required to provide the service rather than being collected to build advertising profiles from private communication.
5. Contacts and contact discovery
Signal can optionally help determine which contacts in a device address book also use Signal. The service uses a contact-discovery system intended to reduce exposure of the address book during that process.
Signal explains that contact information may be cryptographically processed and transmitted in order to determine whether a contact is registered. Contact discovery is separate from the contents of encrypted conversations.
6. Support information
If a user contacts Signal support, information voluntarily provided in the support request may be used to investigate the issue and respond to that case. Signal states that personal information shared with support is kept for the purpose of researching and resolving the support request.
7. Managing account and privacy information
Users can manage profile and privacy-related information through Signal settings. Available controls include profile details, phone number privacy options, linked devices, account protection features, and other settings supported by the current app version.
Signal PIN and Registration Lock are account-protection features. They should not be confused with message-history backups, device passcodes, or end-to-end encryption keys used during conversations.
8. Third-party providers and services
Signal works with third-party providers for limited operational tasks. One example is delivering a registration verification code to a phone number. Those providers operate under their own privacy obligations for the services they perform.
If users interact with external services through or alongside Signal, such as third-party media or content providers, the terms and privacy practices of those external services apply to those interactions.
9. Situations where information may be disclosed
Signal states that information may be disclosed when necessary to comply with applicable law, regulation, legal process, or an enforceable governmental request. Information may also be used or disclosed when needed to enforce applicable terms, address fraud or security issues, or protect the rights, property, or safety of Signal, its users, or the public as permitted by law.
These disclosure circumstances do not change the technical fact that Signal says it cannot decrypt message or call content protected by end-to-end encryption.
10. Data monetization and advertising
Signal states that it does not sell, rent, or monetize personal data or content. Its service is not funded by targeted advertising based on private conversations, and its published privacy model does not depend on analyzing message content for advertising profiles.
11. Changes to the privacy policy
Signal may revise its privacy policy when needed to keep the terms current and accurate. Continued use of Signal after an update is treated according to the terms stated in the revised policy.
The Signal privacy policy currently published by Signal identifies May 25, 2018 as its effective and updated date. Product features and supporting privacy controls have continued to evolve since that date, so current product behavior should also be read together with Signal’s current support information.
12. Privacy questions
Signal lists [email protected] for questions about its privacy policy. Privacy-related questions about account behavior, phone number visibility, device linking, or specific product settings may also depend on the current Signal version and the settings enabled on each device.