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O-3PO stands for Open-source Open-access Overlay Publishing Option, it intends to make publishing of open-access arXiv overlay journals on WordPress powered websites as easy as possible.

O-3PO powers the website of Quantum - the open journal for quantum science and was originally developed for this purpose.


This is beta software, which still may contain site-specific and/or not well tested code.


O-3PO offers the following features:

  • Automatic download of LaTeX source code and PDF from the arXiv
  • Automatic extraction of meta-data
  • Automagic interpretation of references and DOI links
  • DOI registration with Plan S compliant rich meta-data deposits including bibliography and funder information
  • Xited-by data retrieval from Crossref REST API and NASA ads
  • Merging of cited-by information from multiple sources and bibliometrics calculation
  • Meta-data deposition at the DOAJ API
  • Article source and pdf download as well as meta-data extraction from, as well as journal reference feed for the arXiv
  • Meta-data and full text deposition in the CLOCKSS archive
  • Posting of updates on publications to the queue
  • Linking to Fermat's library
  • Automatic and customizable emails for author communication
  • Search centered navigation of articles
  • Integration of publications in to RSS feed
  • Presentation of journal content by volume
  • Web-statement endpoint for the verification of licenses
  • Transformation of \cite commands in post content into hyperlinks referencing bibliography items
  • Form for the submission of works that are ready to publish by the authors, including various sanity checks and collection of additional meta data
  • Queuing system for manuscripts awaiting publication
  • Functionality for the generation of invoices

Works best with

In fact, certain features of O-3PO may only work correctly in conjunction with the OnePress theme.


  1. Git clone this repository via: git clone
  2. Copy the o3po directory into your wp-content/plugins/ directory.
  3. Activate the plugin through the Plugins menu of WordPress.


O-3PO uses the PHPUnit testing framework. You can run all tests locally by executing make test.


Please refer to the online documentation to learn about the implementation.

The documentation can be build locally by running make docs.

Bugs, limitations, and to do

  • Move fix_custom_logo_html into separate plug-in
  • Move remaining onepress related customizations into a separate plug-in

Frequently Asked Questions

Why should I use O-3PO?

O-3PO is open source, actively maintained, and allows you to combine all the features of a professional publishing platform, with exactly the integrations an arXiv overlay journal needs, with the power of the worlds most popular blogging platform.

Why the name O-3PO?

It is obviously a play on the name of humanoid robot character from a series of popular science fiction movies, whose primary purpose is to assist people in their communication, just like this plugin.


  1. Various settings can be customized via the settings.



  • Treat .txt files like LaTeX source files because this is what the arXiv seems to be doing
  • More robust error handling for the case of pdf-only arXiv manuscripts
  • Support for ShortDOIs
  • Prevent accidental trashing or deletion of publication posts after public publishing


  • Added shortcodes to generate various lists of contributing people from data that can be specified in the plugin settings
  • Support database cites in cited by data
  • Fix for recognizing certain ways of specifying affiliations from latex source code
  • Ensure that MathML title and absctract are always valid xml


  • Compatibility with PHP 8.0
  • Added form for submission to works ready to publish
  • Added dashboard widget displaying a queue of works awaiting publication
  • Added functionality to generate invoices
  • Correctly handle and display different name style (given name(s) first or last)
  • Improved error handling in interaction with CLOCKSS
  • Updated used Crossref meta-data scheme to version 4.4.2 and include funder information
  • Improved fuzzy identification of DOIs from bibliographies
  • Better handling of LaTeX commands when converting to utf-8
  • Advanced bibliometrics including calculation of a lower bound on the journal impact factor (JIF) from openly available citation data


  • Uncluttered RSS feed content
  • Use button instead of form/input elements for action buttons (full text, print, ...)
  • improved generation of Trackbacks
  • Fixed truncation of formulas when creating excerpts
  • Extract DOIs from ULRs as a fallback also from BibLaTeX bibliographies
  • Minor bug fixes


  • Added maintenance mode.
  • O-3PO is now largely theme independent.
  • Settings page completely redesigned.
  • Email templates and various other aspects of the plugin are now customizable.
  • Tweaked appearance of publications.
  • Code quality and test coverage improved.
  • Improved cited-by data parsing.
  • Support for https api
  • Greatly improved documentation of settings
  • Better test coverage
  • Support for \cite commands and improved parsing of \affiliation macros


  • Settings page now uses password text fields for sensitive settings.
  • Fixed file name of full text pdf download.


  • Fix for an additional incompatibility with PHP >=7.1.
  • Restrict visible indication of test system to adminbar to allow setup on production system.


  • Now compatible with and tested on multiple PHP versions ranging from 5.6 to 7.2.8.
  • CLOCKSS interface activated.
  • Search page template with extra feedback to users can now be deactivated in settings.
  • Many smaller bug fixes.
  • Test coverage massively increased.


  • First publicly available version.


The WordPress Plugin O-3PO is licensed under the GPL v3 or later.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2, as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

A copy of the license is included in the root of the plugin’s directory. The file is named license.


This plugin is based on the structure provided by the WordPress-Plugin-Boilerplate.