The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

You can use plugins to customize the behavior of OCRmyPDF at certain points of interest.

Currently, it is possible to:

  • add new command line arguments
  • override the decision for whether or not to perform OCR on a particular file
  • modify the image is about to be sent for OCR
  • modify the page image before it is converted to PDF
  • replace the Tesseract OCR with another OCR engine that has similar behavior
  • replace Ghostscript with another PDF to image converter (rasterizer) or PDF/A generator

OCRmyPDF plugins are based on the Python pluggy package and conform to its conventions. Note that: plugins installed with as setuptools entrypoints are not checked currently, because OCRmyPDF assumes you may not want to enable plugins for all files.

Script plugins

Script plugins may be called from the command line, by specifying the name of a file. Script plugins may be convenient for informal or “one-off” plugins, when a certain batch of files needs a special processing step for example.

ocrmypdf --plugin input.pdf output.pdf

Multiple plugins may be installed by issuing the --plugin argument multiple times.

Packaged plugins

Installed plugins may be installed into the same virtual environment as OCRmyPDF is installed into. They may be invoked using Python standard module naming. If you are intending to distribute a plugin, please package it.

ocrmypdf --plugin ocrmypdf_fancypants.pockets.contents input.pdf output.pdf

OCRmyPDF does not automatically import plugins, because the assumption is that plugins affect different files differently and you may not want them activated all the time. The command line or ocrmypdf.ocr(plugin='...') must call for them.

Third parties that wish to distribute packages for ocrmypdf should package them as packaged plugins, and these modules should begin with the name ocrmypdf_ similar to pytest packages such as pytest-cov (the package) and pytest_cov (the module).


We strongly recommend plugin authors name their plugins with the prefix ocrmypdf- (for the package name on PyPI) and ocrmypdf_ (for the module), just like pytest plugins.

Setuptools plugins

You can also create a plugin that OCRmyPDF will always automatically load if both are installed in the same virtual environment, using a setuptools entrypoint.

Your package’s would need to contain the following, for a plugin named ocrmypdf-exampleplugin:

# sample ./ file
from setuptools import setup

    # the following makes a plugin available to pytest
    entry_points={"ocrmypdf": ["exampleplugin = exampleplugin.pluginmodule"]},

Plugin requirements

OCRmyPDF generally uses multiple worker processes. When a new worker is started, Python will import all plugins again, including all plugins that were imported earlier. This means that the global state of a plugin in one worker will not be shared with other workers. As such, plugin hook implementations should be stateless, relying only on their inputs. Hook implementations may use their input parameters to to obtain a reference to shared state prepared by another hook implementation. Plugins must expect that other instances of the plugin will be running simultaneously.

The context object that is passed to many hooks can be used to share information about a file being worked on. Plugins must write private, plugin-specific data to a subfolder named {options.work_folder}/ocrmypdf-plugin-name. Plugins MAY read and write files in options.work_folder, but should be aware that their semantics are subject to change.

OCRmyPDF will delete options.work_folder when it has finished OCRing a file, unless invoked with --keep-temporary-files.

The documentation for some plugin hooks contain a detailed description of the execution context in which they will be called.

Plugins should be prepared to work whether executed in worker threads or worker processes. Generally, OCRmyPDF uses processes, but has a semi-hidden threaded argument that simplifies debugging.

Plugin hooks

A plugin may provide the following hooks. Hooks must be decorated with ocrmypdf.hookimpl, for example:

from ocrmpydf import hookimpl

def add_options(parser):

The following is a complete list of hooks that are available, and when they are called.

Note on firstresult hooks

If multiple plugins install implementations for this hook, they will be called in the reverse of the order in which they are installed (i.e., last plugin wins). When each hook implementation is called in order, the first implementation that returns a value other than None will “win” and prevent execution of all other hooks. As such, you cannot “chain” a series of plugin filters together in this way. Instead, a single hook implementation should be responsible for any such chaining operations.

Custom command line arguments

Execution and progress reporting

Applying special behavior before processing

PDF page to image

Modifying intermediate images

OCR engine

PDF/A production