iMessage vs Signal: Both E2EE by Default, But Only One Is Auditable
iMessage and Signal both encrypt every chat by default. That's the good news. The bad news: iMessage is locked to Apple devices (Android users fall back to unencrypted SMS), the encryption implementation is closed source, and iCloud backups contain plaintext messages unless you opt into Advanced Data Protection. Signal is cross-platform, open source, and backed up nowhere. Here's the honest comparison.
Security comparison: 13 dimensions
| Dimension | Signal | iMessage |
|---|---|---|
| Default end-to-end encryption | Every chat, call, group, status — always on, not opt-in | Yes — every iMessage chat, call, group is end-to-end encrypted between Apple devices |
| Encryption protocol | ★ Signal Protocol (Double Ratchet) — open source, audited by dozens of independent teams | Apple proprietary (RSA + AES) — closed source, no third-party audit of full implementation |
| Metadata collection | ★ Minimal — sealed sender hides who is messaging whom; only phone + last connection date stored | Significant — Apple ID, contacts, device list, timestamps. iCloud backups contain plaintext messages unless Advanced Data Protection is enabled |
| Cloud backups (E2EE?) | ★ No cloud backups — Signal deliberately does not back up messages anywhere | NO — iCloud Messages backup is encrypted but Apple holds keys. OPT-IN Advanced Data Protection (2022) makes backups E2EE |
| Open source | ★ Fully open source — clients AND server on GitHub, anyone can audit | Closed source — no public code |
| Independent audits | ★ Multiple ongoing third-party audits (NCC Group, Quarkslab, others); results published | Apple publishes security whitepapers; no third-party audit of full implementation |
| Platforms supported | ★ iOS / Android / Desktop (Windows/Mac/Linux) / Web | iOS / iPadOS / macOS / visionOS only. Android/Windows/Linux users see green bubble SMS/MMS fallback (unencrypted) |
| Group chat E2EE | ★ Always on (up to 1,000) | Yes (up to 32 / 100) |
| Identity required | Yes (since 2024 optional username, but account still bound to real number) | Apple ID required (typically email-based) |
| Multi-device | Up to 5 linked devices — E2EE preserved, primary phone is source of truth | All Apple devices linked to same iCloud account — full sync |
| Government data requests | Publishes transparency reports; in recent 12 months ~2,230 subpoenas, mostly for "registration date" only | Apple publishes transparency reports (~150 countries; 6+ requests per device in 2023 reports) |
| Disappearing messages | ★ Yes, custom timers from 30 seconds to 4 weeks | No native disappearing messages |
| Approx. monthly active users | ~70 million | ★ ~1 billion (iMessage users, US-centric) |
★ marks the dimension where one app clearly wins on security.
Sources: Signal official docs,
Apple iMessage Security Guide,
Apple Transparency Report (2023), Signal Transparency Reports (2024).
Who should pick which
Choose Signal if security and openness matter
- You have Android users in your contacts (iMessage forces them to green-bubble SMS/MMS)
- You want open-source transparency — anyone can audit Signal's encryption
- You want metadata minimization — sealed sender, no social graph stored
- You need larger group chats (1,000 vs 32/100)
- You're a journalist, activist, lawyer — anyone whose security model is "I want to verify the cryptography myself"
iMessage is fine if you live in Apple's ecosystem
- All your contacts are on iPhones and Macs — the blue-bubble network effect is real
- You prefer Apple's UI polish, Memoji, screen effects, FaceTime integration
- You've turned on Advanced Data Protection for iCloud (so backups are also E2EE)
- You don't have a high-risk threat model — you trust Apple's privacy marketing
- You accept that the encryption implementation is closed source and not independently audited
The default-encryption tie that masks five real differences
iMessage and Signal both encrypt every chat by default. On a strict cryptography comparison, the headlines look similar. But "is the message encrypted in transit" is only one of seven things that determine whether a messenger is actually secure. On the other six — metadata, backups, open-source transparency, cross-platform availability, auditability, and metadata minimization — the two messengers diverge sharply.
1. Cross-platform: where iMessage loses by design
iMessage works only on Apple devices: iPhone, iPad, Mac, Apple Vision Pro. There is no iMessage client for Android, Windows, Linux, or the web. When an iPhone user texts an Android user, the message falls back to SMS / MMS — which is unencrypted plaintext sent over carrier networks. This is the infamous "green bubble" problem, and it's not just a UX issue. It's a security gap: any time you message an Android contact from iMessage, your message is sent in the clear.
Signal works on every platform. iOS, Android, Windows, macOS, Linux, and even a desktop app. If your contact has any modern device, you can message them with E2EE on. This makes Signal the only viable choice for cross-platform encrypted communication.
2. iCloud backups: the silent iMessage security hole
iMessage messages are backed up to iCloud by default — and those backups are encrypted but Apple holds the keys. If Apple receives a subpoena or a data request, or if a rogue employee accesses your backup, your message history is exposed. Apple explicitly says so in their security guide: "Apple can access iCloud data when needed, for example, to help you restore your account."
In December 2022, Apple introduced Advanced Data Protection (ADP), an opt-in feature that makes iCloud backups end-to-end encrypted. If you turn ADP on, even Apple can't read your messages. But ADP is off by default, and most users don't enable it. If you use iMessage without ADP, your messages are effectively recoverable by Apple — and by anyone who can compel Apple.
Signal's design avoids this entirely: Signal does not back up your messages anywhere. If you lose your phone, you lose the message history (unless you've explicitly transferred via the device-to-device migration tool). This is inconvenient but means there's no plaintext backup lying around for anyone to recover.
3. Open source: auditable vs. trust-me
Signal's clients and server are on GitHub. Anyone — academic researchers, security firms, hobbyists — can read the code that handles encryption, metadata minimization, and message routing.
iMessage is closed source. Apple publishes a security whitepaper describing the protocol at a high level, but the actual implementation is hidden. You have to trust that the encryption matches what the whitepaper claims. There's no way for an independent researcher to verify.
For cryptography specifically, this matters because encryption bugs are common. Apple's iMessage has had multiple high-profile vulnerabilities over the years (Citizen Lab documented exploits used against activists and journalists). Signal's open-source code has had its own bugs, but they were caught and fixed quickly because anyone could audit.
4. Metadata: sealed sender vs. full contact map
Signal's sealed-sender protocol hides who is messaging whom from Signal's servers. Apple has no equivalent. Apple's iCloud infrastructure knows who sent what to whom, when, on what device, and from what IP address. This metadata is recoverable from iCloud backups (without ADP) and is part of Apple's response to government data requests.
In their 2023 transparency report, Apple disclosed receiving tens of thousands of device requests across ~150 countries, the vast majority producing some disclosure. Signal's per-user request volume is much lower, partly because there's less metadata to hand over.
5. Disappearing messages and security extras
Signal has built-in disappearing messages with custom timers from 30 seconds to 4 weeks. iMessage has no native equivalent. iOS 17 added some features around message retention, but they don't match Signal's mature disappearing-message implementation.
Signal also ships sealed sender by default, anonymous forward-secrecy ratchets, screen security (block screenshots in recents), and a "view-once" media mode. iMessage has some of these (e.g., iOS 16+ adds "Message Search" improvements), but the overall security-extras surface area is smaller.
6. The political and economic dimension
Signal is run by a 501(c)(3) nonprofit funded by donations. It has no advertising business, no interest in monetizing your data, and a track record of resisting government pressure (including a subpoena fight in 2021 that Signal publicized). Apple is a $3 trillion company whose business depends on selling devices and locking users into its ecosystem. Apple's privacy marketing is genuine, but Apple also has structural incentives that a nonprofit like Signal does not.
Where iMessage is genuinely good
None of the above means iMessage is bad. iMessage's encryption is real, Apple's privacy marketing has driven industry-wide improvements, and Advanced Data Protection (when enabled) closes the backup gap. For users who live entirely in Apple's ecosystem and have ADP turned on, iMessage is materially private.
The blue-bubble network effect is also a real benefit: if all your contacts are on iPhones, the friction of convincing them to install Signal is real, and iMessage just works out of the box. For casual users with no elevated threat model, iMessage is a reasonable default.
Reddit consensus (r/privacy, r/apple, r/signal)
r/privacy generally prefers Signal for sensitive communication and accepts iMessage as "fine for everyday use, but turn on Advanced Data Protection." r/apple tends to defend iMessage as "encrypted, easy, integrated" while acknowledging the closed-source limitation. r/signal points out that the green-bubble fallback to SMS is a real security issue when messaging Android users.
Verdict
Both iMessage and Signal are end-to-end encrypted by default. The differences are: Signal is cross-platform, open source, audit-friendly, has minimal metadata, and has no cloud backups. iMessage is locked to Apple, closed source, has iCloud backup risks unless ADP is on, and has richer metadata exposure. For security and openness, Signal wins. For UX and Apple-ecosystem integration, iMessage wins.