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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 at and cited-by retrieval from Crossref REST API
  • Meta-data deposition at the DOAJ API
  • Article source and pdf download as well as meta-data extraction from, and 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
  • Cited-by information retrieval from NASA ads
  • Merging of cited-by information from multiple sources and bibliometrics calculation
  • 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 into hyperlinks referencing bibliography items

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.



  • 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.