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Home > Signal Knowledge Base

Signal Knowledge Base

Answers to frequently asked questions about Signal Messenger

Basics

  • How to install Signal?
  • What are the phone or system requirements for Signal?
  • Can I use Signal without a phone number?
  • Can I use Signal on multiple phones?
  • Does Signal work with dual SIM phones?
  • Can I use Signal on a PC, desktop computer, laptop, tablet, or iPad?
  • What are Linked devices on Signal?
  • What do the check marks or the spinning circle mean in Signal messages?
  • What do the two filled check marks on Signal mean?
  • Have I been blocked on Signal?
  • What is a safety number on Signal?
  • What is a message request on Signal and what should I do with it?
  • Can I use Signal for work?
  • Can I download and install the Signal APK for Android?
  • Does Signal have channels in the app?
  • Can I make a broadcast list in Signal?
  • Can I send messages from WhatsApp to Signal, or vice versa?

Signal App Tips voor meer Veiligheid, Beveiliging en Privacy

Signal Messenger User Guide

Learn how to download Signal, explore its basic features, and make the most of its privacy tools and helpful tips.

Latest news.

Signal brings on-device backups for iPhone and iPad to beta

Signal brings on-device backups for iPhone and iPad to beta

With support for local backups, Signal now offers multiple backup options on iOS.

Signal now lets you record much longer videos in the app

Signal now lets you record much longer videos in the app

Signal has increased the maximum length of in-app video recordings.

Signal makes iPhone-to-iPhone account transfers much faster with Wi-Fi Aware

Signal makes iPhone-to-iPhone account transfers much faster with Wi-Fi Aware

Signal now uses Wi-Fi Aware for faster and more reliable device transfers.

More news >

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Username Privacy
  • Unlike other messaging apps, Signal cannot easily see or produce the usernames of given accounts.
  • Usernames in Signal are protected using a custom Ristretto 25519 hashing algorithm and zero-knowledge proofs.
Link Previews and Privacy
  • Some messaging apps handle link previews in a highly insecure manner.
  • Instead of generating the link preview locally on the user’s own device, these apps choose to send links to a hosted service and generate the link preview remotely instead.
  • This puts the remote link preview service in a position where it can see and potentially monitor which links people are sharing, who is sharing them, and when they were shared.
Telegram Link Previews
  • Link Previews in Telegram are always generated remotely on Telegram’s servers.
  • Telegram provides an option to completely disable Link Previews in Secret Chats. If this setting isn’t disabled, even URLs and websites that are exchanged in end-to-end encrypted chats are leaked to Telegram’s servers.
    • iOS: Telegram Settings > Privacy and Security > Data Settings > Link Previews
    • Android: Telegram Settings > Privacy and Security > Link Previews
WhatsApp Multi-Device Support
  • WhatsApp Desktop is available for macOS and Windows.
  • WhatsApp Web can run in the web browser on other platforms.
    • The WhatsApp Code Verify web browser extension must be installed in order to mitigate possible man-in-the-middle attacks.
Telegram Multi-Device Support
  • Only “Cloud Chats” (which are not end-to-end encrypted) remain in sync across mobile and desktop.
  • Telegram Secret Chats are not synchronized across devices.
Telegram Reactions
  • Reactions are completely disabled in Telegram’s optional end-to-end encrypted Secret Chats.
Telegram Voice Notes
  • Voice notes outside of Secret Chats are not end-to-end encrypted.
  • Telegram Premium users can access a Voice-to-Text Conversion feature.
    • These transcriptions are generated remotely (and therefore insecurely) on Telegram’s servers using their voice message transcription API.
Telegram Call Verification
  • Telegram users need to look at a “key visualization” and manually verify four emoji characters at the beginning of every call.
    • If this step is ever skipped, that conversation is at risk of being intercepted by a man-in-the-middle attack.
  • One-on-one video calls in Telegram have only been end-to-end encrypted since August 2020.
Google Messages Multi-Device Support
  • Messages for Web can relay messages between a phone and a web browser.
    • No browser extension is available to verify the evaluated code, so man-in-the-middle attacks are a possibility.
    • Messages for Web supports legacy message formats (e.g. SMS and MMS) that are not end-to-end encrypted.
  • No desktop apps are available.
Google Messages and Calling
  • Google Messages doesn’t include support for voice and video calls.
  • Google Meet is a separate application that can optionally be installed on the same phone.
    • End-to-end encryption for voice and video calls can be enabled in Google Meet under certain conditions.
Google Messages End-to-end Encryption
  • End-to-end encryption is only enabled for Rich Communication Services (RCS) chats, and only if everyone in the conversation is also using the Google Messages app.
    • End-to-end encryption is not enabled when exchanging messages with other RCS apps (e.g. Samsung Messages).
  • Legacy message formats like SMS and MMS are not end-to-end encrypted.
Apple Messages End-to-end Encryption
  • End-to-end encryption is only enabled by default for iMessage (blue bubbles).
  • Legacy message formats like SMS and MMS (green bubbles) are not end-to-end encrypted.
  • Apple can also access end-to-end encrypted chats and reveal message contents to external parties under some circumstances.
    • To prevent this, every participant in the conversation must either enable Advanced Data Protection for iCloud or completely turn off iCloud backups on all of their devices.
    • More information is available in Apple’s iCloud data security overview.
Signal Group Permissions

In addition to other group attributes that are end-to-end encrypted (such as group names, group descriptions, and group avatars), the Signal service also doesn’t have access to any information about which accounts are part of a group, which accounts are admins in a group, which accounts can add new people to a group, which accounts can approve requests to join a group, or which accounts can send messages in a group.