Delta Chat

Delta Chat is a messaging app for mobile and desktop, available on Android, iOS, Linux, macOS, Windows, and self-hosted setups. It is free, with no free trial. The app supports multiple profiles and devices, using chatmail relays to carry messages. Messages are end-to-end encrypted by default, including attachments and their metadata, using a subset of OpenPGP with Secure-Join and Autocrypt. The project says its encryption and network components have undergone multiple independent security audits, including audits in 2024. Servers can still see sender and receiver addresses and message size; other message, contact, and group metadata is encrypted. Chats can include interactive web apps for gaming and collaboration. Audio and video calls are available on Android and iOS through peer-to-peer WebRTC, but a March 2026 post said the feature was still behind a debug setting. Classic email addresses can be used as relays only when used exclusively by chatmail clients, and classic email providers generally do not support push notifications. The FAQ says there are no immediate plans for a web client; the project links to a forum for support and feedback.

Delta Chat offers free, cross-platform messaging with default encryption and in-chat web apps. Note the visible server metadata, limitations on classic email relays, and the reported status of calls and web access.

Delta Chat may suit people looking for free messaging across mobile and desktop, with default end-to-end encryption and support for multiple profiles or devices. It may also fit users who want interactive web apps in chats or can use chatmail relays.

Delta Chat is a free, open-source messenger that uses interoperable chatmail relays instead of a conventional central service. It suits privacy-focused people who need encrypted chats across phones and computers, provided they can accept exposed addressing metadata and no browser client. Its default encryption and multi-device design are compelling, but unfinished calling and relay limitations make it less universal than mainstream messengers.

Overview

Delta Chat is maintained as an open-source community project, with merlinux GmbH in Freiburg, Germany responsible for website content. It supports multiple profiles and devices, so one installation can separate identities or keep conversations available across a phone and desktop. Messages travel through secure, interoperable chatmail relays, giving the service a decentralized foundation rather than tying users to one provider.

Encryption is enabled by default for messages, attachments and attachment metadata. The app uses a secure subset of OpenPGP, with Secure-Join and Autocrypt helping establish end-to-end encrypted conversations. The project reports multiple independent audits of its encryption and network components, including audits in 2024. This protects conversation content well, but does not make relay traffic anonymous: servers can see sender and receiver addresses and message size, while other message, contact and group metadata is encrypted.

Key features

Messaging and integrations

Multi-profile and multi-device support is valuable for people who separate personal, work or community conversations. Chatmail relays provide the intended transport, while in-chat web apps add interactive experiences for gaming and collaboration without leaving a conversation.

A classic email address can act as a relay, but only when it is used exclusively by chatmail clients. Conventional email providers generally do not provide push notifications, so this fallback can mean slower or less convenient message delivery. Delta Chat therefore works best when everyone involved uses compatible chatmail-oriented clients.

Calls and data protection

Audio and video calls on Android and iOS use peer-to-peer WebRTC, with signaling carried through Delta Chat messages. The feature was still behind a debug setting in March 2026, so calling should be treated as experimental rather than a dependable replacement for an established calling app.

There are no encrypted backups, an important drawback for anyone who expects a simple recovery path after losing a device. The FAQ also says there are no immediate plans for a web client. Users who cannot install software are directed toward portable Windows or Linux AppImage clients instead, which is less convenient than signing in from a browser.

Pricing

The Delta Chat plan costs free and is free and open-source software. There is no free trial because the product itself is free, and no paid tier, seat charge or usage quota is stated. That makes it suitable for individuals, families and small groups who want the full client without a subscription. It also means there is no commercial plan offering hosted convenience, managed recovery or enhanced support.

Platforms

Delta Chat has apps for Android, iOS, Linux, macOS and Windows, and can be self-hosted. Its broad desktop and mobile coverage benefits households and teams moving between operating systems. The absence of a web client is the main platform limitation; portable Windows and Linux AppImage builds are the stated workaround when installation is restricted.

Who it's for

Choose Delta Chat if default end-to-end encryption, open-source development, relay interoperability and multiple profiles or devices matter more than a polished, conventional service. It is particularly suitable for privacy-conscious communities willing to use chatmail relays and accept that servers still observe addresses and message size.

Look elsewhere if browser access, mature voice and video calling, encrypted backups or seamless compatibility with ordinary email users are priorities. The classic-email option has push-notification limitations, and experimental calls are not yet a strong reason to switch from a dedicated calling platform.

Pros and cons

• Pros: End-to-end encryption is on by default and includes attachments and their metadata.
• Pros: Multi-profile and multi-device support accommodates separated identities and cross-device use.
• Pros: Chatmail relays and in-chat web apps provide interoperable messaging plus interactive collaboration or games.
• Pros: The free, open-source plan covers all supported clients without a subscription.
• Cons: Relay servers can see sender and receiver addresses and message size, so encryption does not conceal all metadata.
• Cons: There is no web client and no encrypted-backup feature.
• Cons: Android and iOS calling remained behind a debug setting in March 2026.
• Cons: Classic email relays generally lack push notifications and must be used exclusively by chatmail clients.

Alternatives

Signal is a better fit for users who want free messaging and calling with a mobile account required for desktop. Wire suits readers who want a free tier, web access and a fully open-source codebase. Viber is the broader consumer choice for free messaging and calls to Viber users, with paid Viber Out options.

Crypho suits personal users who need encrypted calls and video calls but can live with a one-group free-plan limit and 3 MB files. Jami is another free, cross-platform project for readers seeking a different decentralized approach. Monal is a free option specifically for iOS and macOS XMPP chat. Olvid offers a free tier with unlimited messages and attachments, secure groups and ephemeral messages. SimpleX Chat is a free alternative for readers who want its AGPLv3-based ecosystem and self-hosting support.

The Secure Messaging Apps and Encrypted Messaging Apps lists provide broader comparisons.

Verdict

Delta Chat is a strong choice for privacy-minded users who want free, open-source encrypted messaging across mobile and desktop, especially when multi-profile use and chatmail interoperability matter. Choose another app if you need a browser client, encrypted backups, dependable calls today or metadata protection beyond message content.