Release lifecycle

This page details the release lifecycle for the Zulip server and client-apps, well as our policies around backwards-compatibility and security support policies. In short:

• We recommend always running the latest releases of the Zulip clients and servers. Server upgrades are designed to Just Work; mobile and desktop client apps update automatically.
• The server and client apps are backwards and forwards compatible across a wide range of versions. So while it's important to upgrade the server to get security updates, bug fixes, and new features, the mobile and desktop apps will continue working for at least 18 months if you don't do so.
• New server releases are announced via the low-traffic zulip-announce email list. We highly recommend subscribing so that you are notified about new security releases.
• Zulip Cloud runs the branch that will become the next major server/web app release, so it is always "newer" than the latest stable release.

Server and web app

The Zulip server and web app are developed together in the Zulip server repository.

Stable releases

• Zulip Server stable releases, such as Zulip 4.5. Organizations self-hosting Zulip primarily use stable releases.
• The numbering scheme is simple: the first digit indicates the major release series (which we'll refer to as "4.x"). (Before Zulip 3.0, Zulip versions had another digit, e.g. 1.9.2 was a bug fix release in the Zulip 1.9.x major release series).
• New major releases, like Zulip 4.0, are published every 3-6 months, and contain hundreds of features, bug fixes, and improvements to Zulip's internals.
• New maintenance releases, like 4.3, are published roughly once a month. Maintenance releases are designed to have no risky changes and be easy to reverse, to minimize stress for administrators. When upgrading to a new major release series, We recommend always upgrading to the latest maintenance release in that series, so that you use the latest version of the upgrade code.

Starting with Zulip 4.0, the Zulip web app displays the current server version in the gear menu. With older releases, the server version is available via the API.

This ReadTheDocs documentation has a widget in the lower-left corner that lets you view the documentation for other versions. Other documentation, like our Help Center, API documentation, and Integrations documentation, are distributed with the Zulip server itself (E.g. https://zulip.example.com/help/).

Git versions

Many Zulip servers run versions from Git that have not been published in a stable release.

• Zulip Cloud essentially runs the master branch. It is usually a few days behind master (with some cherry-picked bug fixes), but can fall up to 2 weeks behind when major UI or internals changes mean we'd like to bake changes longer on chat.zulip.org before exposing them to the full Zulip Cloud userbase.
• chat.zulip.org, the bleeding-edge server for the Zulip development community, is upgraded to master several times every week. We also often "test deploy" changes not yet in master to chat.zulip.org to facilitate design feedback.
• We maintain Git branches with names like 4.x containing backported commits from master that we plan to include in the next maintenance release. Self hosters can upgrade to these stable release branches to get bug fixes staged for the next stable release (which is very useful when you reported a bug whose fix we choose to backport). We support these branches as though they were a stable release.
• Self-hosters who want new features not yet present in a major release can upgrade to master or run a fork of Zulip.

Compatibility and upgrading

A Zulip design goal is for there never to be a reason to run an old version of Zulip. We work extremely hard to make sure Zulip is stable for self-hosters, has no regressions, and that the Zulip upgrade process Just Works.

The Zulip server and clients apps are all carefully engineered to ensure compatibility with old versions. In particular:

• The Zulip mobile and desktop apps maintain backwards-compatibility code to support any Zulip server since 2.1.0. (They may also work with older versions, with a degraded experience).
• Zulip maintains an API changelog detailing all changes to the API to make it easy for client developers to do this correctly.
• The Zulip server preserves backwards-compatibility in its API to support versions of the mobile and desktop apps released in roughly the last year. Because these clients auto-update, generally there are only a handful of active clients left by the time we desupport a version.

As a result, we generally do not backport changes to previous stable release series except in rare cases involving a security issue or critical bug just after publishing a major release.

Security releases

When we discover a security issue in Zulip, we publish a security and bug fix release, transparently documenting the issue(s) using the industry-standard CVE advisory process.

When new security releases are published, we simultaneously publish the fixes to the master and stable release branches (E.g. 4.x), so that anyone using those branches can immediately upgrade as well.

See also our security model documentation.

Upgrade nag

Starting with Zulip 4.0, the Zulip web app will display a banner warning users of a server running a Zulip release that is more than 18 months old. We do this for a few reasons:

• It is unlikely that a server of that age is not vulnerable to a security bug in Zulip or one of its dependencies.
• The Zulip mobile and desktop apps are only guaranteed to support server versions less than 18 months old.

The nag will appear only to organization administrators starting a month before the deadline; after that, it will appear for all users on the server.

You can adjust the deadline for your installation by setting e.g. SERVER_UPGRADE_NAG_DEADLINE_DAYS = 30 * 21 in /etc/zulip/settings.py and then restarting the server.

Operating system support

For platforms we support, like Debian and Ubuntu, Zulip aims to support all versions of the upstream operating systems that are fully supported by the vendor. We document how to correctly upgrade the operating system for a Zulip server, including how to correctly chain upgrades when the latest Zulip release no longer supports your OS.

Note that we consider Ubuntu interim releases, which only have 8 months of security support, to be betas, not releases, and do not support them in production.

Server roadmap

The Zulip server project uses several GitHub labels to structure communication within the project about priorities:

• The high priority label tags issues that we consider important. This label is meant to be a determination of importance that can be done quickly and then used as an input to planning processes.
• The release goal label is used for work that we hope to include in the next major release. The related post release label is used to track work we want to focus on shortly after the next major release.

The Zulip community feels strongly that all the little issues are, in aggregate, just as important as the big things. Most resolved issues do not have any of these priority labels.

We welcome participation from our user community in influencing the Zulip roadmap. If a bug or missing feature is causing significant pain for you, we'd love to hear from you, either in chat.zulip.org or on the relevant GitHub issue. Please an include an explanation of your use case: such details can be extremely helpful in designing appropriately general solutions, and also helps us identify cases where an existing solution can solve your problem. See Reporting issues for more details.

Client apps

Zulip's client apps officially support all Zulip server versions (and Git commits) released in the previous 18 months, matching the behavior of our upgrade nag.

• The Zulip mobile apps release new versions from the development branch frequently (usually every couple weeks). Except when fixing a critical bug, releases are first published to our beta channels.

• The Zulip desktop apps are implemented in Electron, the browser-based desktop application framework used by essentially all modern chat applications. The Zulip UI in these apps is served from the Zulip server (and thus can vary between tabs when it is connected to organizations hosted by different servers).

The desktop apps automatically update soon after each new release. Because Zulip's desktop apps are implemented in Electron and thus contain a Chromium browser, security-conscious users should leave automatic updates enabled or otherwise arrange to promptly upgrade all users after a new security release.

New desktop app releases rarely contain new features, because the desktop app tab inherits its features from the Zulip server/web app. However, it is important to upgrade because they often contain important security or OS compatibility fixes from the upstream Chromium project.

The Zulip server supports blocking access or displaying a warning to users attempting to access the server with extremely old or known insecure versions of the Zulip desktop and mobile apps, with an error message telling the user to upgrade.

API bindings

The Zulip API bindings and related projects maintained by the Zulip core community, like the Python and JavaScript bindings, are released independently as needed.

https://github.com/zulip/zulip/issues?q=is%3Aissue+is%3Aopen+label%3A%22priority%3A+blocker%22

https://github.com/zulip/zulip/issues?q=is%3Aissue+is%3Aopen+label%3A%22priority%3A+high%22

https://github.com/zulip/zulip/issues?q=is%3Aissue+is%3Aopen+label%3A%22release+goal%22

https://github.com/zulip/zulip/issues?q=is%3Aissue+is%3Aopen+label%3A%22post+release%22