Paperless-ngx Development

This section describes the steps you need to take to start development on paperless-ngx.

Check out the source from github. The repository is organized in the following way:

  • main always represents the latest release and will only see changes when a new release is made.

  • dev contains the code that will be in the next release.

  • feature-X contain bigger changes that will be in some release, but not necessarily the next one.

When making functional changes to paperless, always make your changes on the dev branch.

Apart from that, the folder structure is as follows:

  • docs/ - Documentation.

  • src-ui/ - Code of the front end.

  • src/ - Code of the back end.

  • scripts/ - Various scripts that help with different parts of development.

  • docker/ - Files required to build the docker image.

Contributing to Paperless

Maybe you’ve been using Paperless for a while and want to add a feature or two, or maybe you’ve come across a bug that you have some ideas how to solve. The beauty of open source software is that you can see what’s wrong and help to get it fixed for everyone!

Before contributing please review our code of conduct and other important information in the contributing guidelines.

Code formatting with pre-commit Hooks

To ensure a consistent style and formatting across the project source, the project utilizes a Git pre-commit hook to perform some formatting and linting before a commit is allowed. That way, everyone uses the same style and some common issues can be caught early on. See below for installation instructions.

Once installed, hooks will run when you commit. If the formatting isn’t quite right or a linter catches something, the commit will be rejected. You’ll need to look at the output and fix the issue. Some hooks, such as the Python formatting tool black, will format failing files, so all you need to do is git add those files again and retry your commit.

Initial setup and first start

After you forked and cloned the code from github you need to perform a first-time setup. To do the setup you need to perform the steps from the following chapters in a certain order:

  1. Install prerequisites + pipenv as mentioned in Bare metal route

  2. Copy paperless.conf.example to paperless.conf and enable debug mode.

  3. Install the Angular CLI interface:

    $ npm install -g @angular/cli
  4. Install pre-commit

    pre-commit install
  5. Create consume and media folders in the cloned root folder.

    mkdir -p consume media
  6. You can now either …

    • install redis or

    • use the included scripts/ to use docker to fire up a redis instance (and some other services such as tika, gotenberg and a postgresql server) or

    • spin up a bare redis container

      docker run -d -p 6379:6379 --restart unless-stopped redis:latest
  7. Install the python dependencies by performing in the src/ directory.

    pipenv install --dev
  • Make sure you’re using python 3.9.x or lower. Otherwise you might get issues with building dependencies. You can use pyenv to install a specific python version.

  1. Generate the static UI so you can perform a login to get session that is required for frontend development (this needs to be done one time only). From src-ui directory:

    npm install .
    ./node_modules/.bin/ng build --configuration production
  2. Apply migrations and create a superuser for your dev instance:

    python3 migrate
    python3 createsuperuser
  3. Now spin up the dev backend. Depending on which part of paperless you’re developing for, you need to have some or all of them running.

python3 runserver & python3 document_consumer & python3 qcluster
  1. Login with the superuser credentials provided in step 8 at http://localhost:8000 to create a session that enables you to use the backend.

Backend development environment is now ready, to start Frontend development go to /src-ui and run ng serve. From there you can use http://localhost:4200 for a preview.

Back end development

The backend is a django application. PyCharm works well for development, but you can use whatever you want.

Configure the IDE to use the src/ folder as the base source folder. Configure the following launch configurations in your IDE:

  • python3 runserver

  • python3 qcluster

  • python3 document_consumer

To start them all:

python3 runserver & python3 document_consumer & python3 qcluster

Testing and code style:

  • Run pytest in the src/ directory to execute all tests. This also generates a HTML coverage report. When runnings test, paperless.conf is loaded as well. However: the tests rely on the default configuration. This is not ideal. But for now, make sure no settings except for DEBUG are overridden when testing.

  • Coding style is enforced by the Git pre-commit hooks. These will ensure your code is formatted and do some linting when you do a git commit.

  • You can also run black manually to format your code


    The line length rule E501 is generally useful for getting multiple source files next to each other on the screen. However, in some cases, its just not possible to make some lines fit, especially complicated IF cases. Append # NOQA: E501 to disable this check for certain lines.

Front end development

The front end is built using Angular. In order to get started, you need npm. Install the Angular CLI interface with

$ npm install -g @angular/cli

and make sure that it’s on your path. Next, in the src-ui/ directory, install the required dependencies of the project.

$ npm install

You can launch a development server by running

$ ng serve

This will automatically update whenever you save. However, in-place compilation might fail on syntax errors, in which case you need to restart it.

By default, the development server is available on http://localhost:4200/ and is configured to access the API at http://localhost:8000/api/, which is the default of the backend. If you enabled DEBUG on the back end, several security overrides for allowed hosts, CORS and X-Frame-Options are in place so that the front end behaves exactly as in production. This also relies on you being logged into the back end. Without a valid session, The front end will simply not work.

Testing and code style:

  • The frontend code (.ts, .html, .scss) use prettier for code formatting via the Git pre-commit hooks which run automatically on commit. See above for installation. You can also run this via cli with a command such as

    $ git ls-files -- '*.ts' | xargs pre-commit run prettier --files
  • Frontend testing uses jest and cypress. There is currently a need for significantly more frontend tests. Unit tests and e2e tests, respectively, can be run non-interactively with:

    $ ng test
    $ npm run e2e:ci

    Cypress also includes a UI which can be run from within the src-ui directory with

    $ ./node_modules/.bin/cypress open

In order to build the front end and serve it as part of django, execute

$ ng build --prod

This will build the front end and put it in a location from which the Django server will serve it as static content. This way, you can verify that authentication is working.


Paperless is available in many different languages. Since paperless consists both of a django application and an Angular front end, both these parts have to be translated separately.

Front end localization

  • The Angular front end does localization according to the Angular documentation.

  • The source language of the project is “en_US”.

  • The source strings end up in the file “src-ui/messages.xlf”.

  • The translated strings need to be placed in the “src-ui/src/locale/” folder.

  • In order to extract added or changed strings from the source files, call ng xi18n --ivy.

Adding new languages requires adding the translated files in the “src-ui/src/locale/” folder and adjusting a couple files.

  1. Adjust “src-ui/angular.json”:

    "i18n": {
        "sourceLocale": "en-US",
        "locales": {
            "de": "src/locale/",
            "nl-NL": "src/locale/messages.nl_NL.xlf",
            "fr": "src/locale/",
            "en-GB": "src/locale/messages.en_GB.xlf",
            "pt-BR": "src/locale/messages.pt_BR.xlf",
            "language-code": "language-file"
  2. Add the language to the available options in “src-ui/src/app/services/settings.service.ts”:

    getLanguageOptions(): LanguageOption[] {
        return [
            {code: "en-us", name: $localize`English (US)`, englishName: "English (US)", dateInputFormat: "mm/dd/yyyy"},
            {code: "en-gb", name: $localize`English (GB)`, englishName: "English (GB)", dateInputFormat: "dd/mm/yyyy"},
            {code: "de", name: $localize`German`, englishName: "German", dateInputFormat: ""},
            {code: "nl", name: $localize`Dutch`, englishName: "Dutch", dateInputFormat: "dd-mm-yyyy"},
            {code: "fr", name: $localize`French`, englishName: "French", dateInputFormat: "dd/mm/yyyy"},
            {code: "pt-br", name: $localize`Portuguese (Brazil)`, englishName: "Portuguese (Brazil)", dateInputFormat: "dd/mm/yyyy"}
            // Add your new language here

    dateInputFormat is a special string that defines the behavior of the date input fields and absolutely needs to contain “dd”, “mm” and “yyyy”.

  3. Import and register the Angular data for this locale in “src-ui/src/app/app.module.ts”:

    import localeDe from '@angular/common/locales/de';

Back end localization

A majority of the strings that appear in the back end appear only when the admin is used. However, some of these are still shown on the front end (such as error messages).

  • The django application does localization according to the django documentation.

  • The source language of the project is “en_US”.

  • Localization files end up in the folder “src/locale/”.

  • In order to extract strings from the application, call python3 makemessages -l en_US. This is important after making changes to translatable strings.

  • The message files need to be compiled for them to show up in the application. Call python3 compilemessages to do this. The generated files don’t get committed into git, since these are derived artifacts. The build pipeline takes care of executing this command.

Adding new languages requires adding the translated files in the “src/locale/” folder and adjusting the file “src/paperless/” to include the new language:

    ("en-us", _("English (US)")),
    ("en-gb", _("English (GB)")),
    ("de", _("German")),
    ("nl-nl", _("Dutch")),
    ("fr", _("French")),
    ("pt-br", _("Portuguese (Brazil)")),
    # Add language here.

Building the documentation

The documentation is built using sphinx. I’ve configured ReadTheDocs to automatically build the documentation when changes are pushed. If you want to build the documentation locally, this is how you do it:

  1. Install python dependencies.

    $ cd /path/to/paperless
    $ pipenv install --dev
  2. Build the documentation

    $ cd /path/to/paperless/docs
    $ pipenv run make clean html

This will build the HTML documentation, and put the resulting files in the _build/html directory.

Building the Docker image

The docker image is primarily built by the GitHub actions workflow, but it can be faster when developing to build and tag an image locally.

To provide the build arguments automatically, build the image using the helper script

Building the docker image from source:

./ Dockerfile -t <your-tag>

Extending Paperless

Paperless does not have any fancy plugin systems and will probably never have. However, some parts of the application have been designed to allow easy integration of additional features without any modification to the base code.

Making custom parsers

Paperless uses parsers to add documents to paperless. A parser is responsible for:

  • Retrieve the content from the original

  • Create a thumbnail

  • Optional: Retrieve a created date from the original

  • Optional: Create an archived document from the original

Custom parsers can be added to paperless to support more file types. In order to do that, you need to write the parser itself and announce its existence to paperless.

The parser itself must extend documents.parsers.DocumentParser and must implement the methods parse and get_thumbnail. You can provide your own implementation to get_date if you don’t want to rely on paperless’ default date guessing mechanisms.

class MyCustomParser(DocumentParser):

    def parse(self, document_path, mime_type):
        # This method does not return anything. Rather, you should assign
        # whatever you got from the document to the following fields:

        # The content of the document.
        self.text = "content"

        # Optional: path to a PDF document that you created from the original.
        self.archive_path = os.path.join(self.tempdir, "archived.pdf")

        # Optional: "created" date of the document. = get_created_from_metadata(document_path)

    def get_thumbnail(self, document_path, mime_type):
        # This should return the path to a thumbnail you created for this
        # document.
        return os.path.join(self.tempdir, "thumb.png")

If you encounter any issues during parsing, raise a documents.parsers.ParseError.

The self.tempdir directory is a temporary directory that is guaranteed to be empty and removed after consumption finished. You can use that directory to store any intermediate files and also use it to store the thumbnail / archived document.

After that, you need to announce your parser to paperless. You need to connect a handler to the document_consumer_declaration signal. Have a look in the file src/paperless_tesseract/ on how that’s done. The handler is a method that returns information about your parser:

def myparser_consumer_declaration(sender, **kwargs):
    return {
        "parser": MyCustomParser,
        "weight": 0,
        "mime_types": {
            "application/pdf": ".pdf",
            "image/jpeg": ".jpg",
  • parser is a reference to a class that extends DocumentParser.

  • weight is used whenever two or more parsers are able to parse a file: The parser with the higher weight wins. This can be used to override the parsers provided by paperless.

  • mime_types is a dictionary. The keys are the mime types your parser supports and the value is the default file extension that paperless should use when storing files and serving them for download. We could guess that from the file extensions, but some mime types have many extensions associated with them and the python methods responsible for guessing the extension do not always return the same value.