Arc vs LINE
Japan's default app — with caveats worth knowing.
LINE applies its custom Letter Sealing encryption to 1:1 and some group messages, but group calls, stickers, reactions, read receipts and bot messages are not end-to-end encrypted, and academic analyses find Letter Sealing lacks forward secrecy. Development ties to Korea (the LINE Plus subsidiary) and NAVER's capital stake also remain. Arc offers audited Signal-Protocol cryptography with forward secrecy and post-quantum protection.
Updated 2026-06-02 · evaluated by Claude Code Opus 4.8 Ultracode
Head-to-head score
Scores from the same independent 9-axis, 100-point rubric used across all 20 messengers. Higher is better.
Arc
89 / 100
LINE
38 / 100
| Axis | Arc | LINE |
|---|---|---|
| Crypto | 18 | 13 |
| Fwd/Bwd Secrecy | 14 | 3 |
| Post-Quantum | 14 | 0 |
| E2EE Coverage | 12 | 9 |
| Sender Privacy | 3 | 0 |
| Registration Privacy | 9 | 4 |
| Ephemeral | 11 | 2 |
| Verification UX | 4 | 4 |
| Multi-Device | 4 | 3 |
Why choose Arc over LINE
01
Forward secrecy and post-compromise security via the Double Ratchet. Researchers (IACR CiC 2026) show LINE's Letter Sealing v2 has neither and is vulnerable to replay and key-compromise-impersonation attacks.
02
Post-quantum cryptography (ML-KEM-1024) — LINE has none — plus IGF and Mutual Burn disappearing messages.
03
Consistent default E2EE across your messages. LINE leaves group calls, stickers, reactions, read receipts and bot messages unencrypted on its servers.
What LINE does well
- Ubiquitous in Japan, with a rich sticker ecosystem, payments, and a broad super-app feature set.
The bottom line
For stickers and everyday reach in Japan, LINE is unmatched. For confidential conversation, Arc (89 vs 38) adds forward secrecy, post-quantum protection, and consistent default E2EE that Letter Sealing does not provide.
Get Arc — E2EE, free for everyone
See the full 20-messenger comparison
How Arc's encryption works