Defining Monorepo Boundaries With Tags

Tags are a way to define boundaries in a monorepo. They are configured in the project.json file of each project, and they affect which projects can depend on each other.

The root .eslintrc.json file specifies our rules for each tag. We recommend reading this article to get up to speed.

Our tag convention

Our tags are split in 2 categories. Generic tags and application tags.

Generic tags

Generic tags are based on the frameworks we use and should be used for simple applications and shared libraries.

These are the generic tags ordered from the most generic to more specific.

TagDescriptionCan depend onCan be depended on by


Basic JS library.


Any project


NodeJS server-side library.

js, node

Any server-side projects.


JS library designed to run in a browser.

js, dom

Any browser-based project.


React library.

js, dom, react

Any react project.


NestJS library.

js, node, nest

NestJS projects.


NextJS library.

js, dom, react, react-next

NextJS projects.


React library using react-router.

js, dom, react, react-spa

React projects using react-router.

Application tags

Simple applications can be tagged with the generic tags above, but applications which have one or more "private" library projects should define their own NX tags, extending one of the generic tags.

It can be one tag which is applied to both the application project and all the associated library projects (like "api"). Or there can be multiple application tags with different rules to segment the library projects (like the "judicial-system" tags).

TagDescriptionCan depend onCan be depended on by


API domain project.

js, node, nest, api, client

Other API projects.


Application system projects

js, dom, react, react-spa, react, application-system, client

Other application system projects


Application system web projects

js, dom, react, react-spa, application-system-web, application-system,

Other application system web projects


Application system api projects

js, node, nest, client, application-system, application-system-api, api,

Other application system api projects


Authentication api projects

js, node, nest, client, auth-api

Other auth APIs


Client projects.

js, node, nest, client

Other clients and application-system


Test projects

js, client, application-system

No one


Judicial system projects

js, judicial-system

Other judicial system projects


Judicial system web projects

js, node, nest, client, judicial-system, judicial-system-api

Other judicial system api projects


Judicial system api projects

js, dom, react, react-spa, judicial-system, judicial-system-web

Other judicial system web projects


Portal project.

js, dom, react, react-spa, portals

Other portal projects.


My pages portal project.

js, dom, react, react-spa, portals, portals-mypages

Other my pages portal projects.


Admin portal project.

js, dom, react, react-spa, portals, portals-admin

Other admin portal projects.

Here is a chart that displays how these tags are connected. Each tag can depend on other tags with a full line arrow pointing to it. Dotted lines represents connections between application tags where a project can depend on the tag but not necessarily other tags further up.

  flowchart BT;
    %% Generic tags
    node & dom --> js
    react --> dom
    react-spa & react-next --> react
    nest --> node

    %% App tags
    judicial-system --> js
    api & auth-api & client & application-system-api & judicial-system-api --> nest
    application-system & application-system-web & portals & portals-admin & portals-mypages & judicial-system-web --> react-spa

    classDef appTag fill:#f9f
    class api,auth-api,client,application-system,application-system-web,application-system-api,portals-admin,portals-mypages,judicial-system-api,judicial-system-web,judicial-system appTag

    %% Shallow dependencies
    api & auth-api -.-> client
    application-system -.-> client
    application-system-api & application-system-web -.-> application-system
    judicial-system-api & judicial-system-web -.-> judicial-system
    portals-mypages & portals-mypages -.-> portals

Tag prefixes

The above tags must be prefixed by one or both of the following prefixes to opt projects into "Can depend on" and "Can be depended on by" rules.

  • scope: - by applying a scope tag to a project, you are saying that ESLint should enforce project boundaries for that project using the "Can depend on" rules documented above.

  • lib: - lib tags describe what kind of project it is to enforce the "Can be depended on by" rules documented above.

All projects must have a "scope" tag and most libraries should have the same tag as "lib" and "scope".

Later we hope to get rid of the "lib" tags and just have "scope" tags. However, first we need to fix or refactor a few tricky projects.


Generic NextJS application:

  "tags": ["scope:react-next"]

React library which works for both NextJS and React SPA projects.

  "tags": ["lib:react", "scope:react"]

NestJS library.

  "tags": ["lib:nest", "scope:nest"]

Fixing module boundary errors

A project tagged with "scope:X" can only depend on libs tagged with "lib:Y", "lib:Z", ... - @nrwl/nx/enforce-module-boundaries

Check which file the code is importing and which tags are configured in the importing project and the imported library.

In some cases, your project should not be importing that library, e.g. it's a library belonging to another application, or you're accidentally importing a server side library from a web project. You should look for ways to refactor your code to not depend on that library. For example, you might move the things you need to another shared library which you are allowed to depend on.

If your project should be able to import that library, then there's some issue with the tags which you need to fix.

Either way, feel free to reach out to the core team and ask for guidance.

External checks: Missing nx tags for project boundaries

Our CI checks that all projects have correct tags. If you get this error, it's likely that you forgot to add a "scope:" tag to a new project.json file. You can re-run the CI check locally by running yarn check-tags.

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