Delta Chat

Delta Chat is a messaging app for people who want encrypted conversations across mobile and desktop without paying a subscription. It is strongest for users comfortable with chatmail relays and the app’s privacy trade-offs. Its default encryption is compelling, but exposed server metadata and no browser client make it a poor fit for everyone.

Overview

Delta Chat routes messages through secure, interoperable chatmail relays and supports multiple profiles and devices. That setup can suit people who want to keep conversations separate or use the app across more than one device. It is an open source community project; merlinux GmbH in Freiburg, Germany is responsible for the website content.

Encryption is on by default for messages, attachments and attachment metadata. Delta Chat uses a secure subset of OpenPGP, with Secure-Join and Autocrypt to establish end-to-end encrypted chats. The project says its encryption and network components have passed multiple independent security audits, including audits in 2024. This is a strong baseline, though not complete metadata privacy: servers can see sender and receiver addresses and message size.

Key features

Messaging and email compatibility

Chatmail relays are the central way to send messages. Delta Chat can also use a classic email address as a relay, but only if that address is used exclusively by chatmail clients. Classic email providers generally do not support push notifications, so this option comes with a meaningful convenience cost and is not a drop-in fit for ordinary email use.

Multiple profiles and devices add useful flexibility, while interactive web apps bring games and collaboration into chats. The app also supports disappearing messages. Encrypted backups are not included, so users who need a protected backup path should weigh that gap before relying on Delta Chat for important conversations.

Calls

Audio and video calls on Android and iOS use peer-to-peer WebRTC, with call signaling carried through Delta Chat messages. The feature was still behind a debug setting in the March 2026 post, so it should not be treated as a settled calling option for everyday use.

Pricing

Delta Chat is free and open source. Its Delta Chat plan costs nothing, with no free trial because there is no paid plan to trial. The plan includes default encryption, a desktop app, voice and video calls, and disappearing messages; encrypted backups are absent. There are no paid tiers or stated seat or quota limits to compare, making cost simple, though users should not mistake free access for a backup feature or fully hidden metadata.

Platforms

Delta Chat supports Android, iOS, Linux, macOS and Windows, as well as self-hosted use. It has no web client, and the FAQ says there are no immediate plans to add one. Users who cannot install software are pointed to portable Windows or Linux AppImage clients instead, which still leaves browser-only users without a supported route. Support and feedback are available through the Delta Chat forum.

Who it's for

Delta Chat is a good match for privacy-conscious users who want default end-to-end encryption, attachments covered by encryption, and multi-device or multi-profile messaging at no charge. Its relay-based approach may also appeal to people who value interoperable infrastructure and in-chat web apps.

Look elsewhere if browser access is essential, if you need encrypted backups, or if you want calls ready for routine use without a debug setting. Users who require servers to be unable to see address and message-size metadata should also consider whether Delta Chat’s protections meet their needs.

Pros and cons

• Pros: Messages, attachments and attachment metadata are encrypted by default, reducing exposure of conversation content.
• Pros: Multiple profiles and devices, plus interactive web apps in chats, support flexible personal and collaborative use.
• Pros: Free and open source across mobile and desktop, with self-hosted use also supported.
• Cons: Servers can see sender and receiver addresses and message size, leaving some metadata exposed.
• Cons: There is no web client, which excludes users who depend on browser-based access.
• Cons: Encrypted backups are not included, and calls remain behind a debug setting in the cited March 2026 post.
• Cons: Classic email relay use requires exclusive use by chatmail clients and generally lacks push notifications.

Alternatives

For a broader comparison, see Secure messaging apps. Choose Jami instead if its free plan and wider platform range, including web, API and extension support, better fit your setup. Olvid is worth considering if you want a free tier with unlimited messages and attachments, secure group discussions and ephemeral messages, plus a free trial.

Wire may suit readers who prioritize a fully open-source codebase available for verification. Crypho is an alternative with a free personal-use plan that caps files at 3mb and groups at one, alongside encrypted calls and video calls. imo offers free calls and messages, though carrier data charges may apply. Keet is another free option with no subscriptions, premium features or ads. Messenger is a free messaging app. Session may fit users seeking open-source encrypted messaging with attachments up to 10mb and no phone number requirement.

Verdict

Choose Delta Chat if you want free messaging with default end-to-end encryption across mobile and desktop, and can accept visible server metadata, no browser client and no encrypted backups. Its main strength is making encryption the default without a subscription; look elsewhere if web access, concealed server metadata or ready-to-use calls matter more.