Derk-jan Hartman - Developer at Wikimedia Foundation

Derk-jan Hartman

Developer at Wikimedia Foundation

Enschede, Overijssel, Netherlands

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Summary

🤩

Rockstar

🎓

Top School

Derk-jan Hartman is a seasoned developer with 23 years of experience building web, mobile and backend systems from the Netherlands, currently working at Baseflow and a long‑standing volunteer contributor to Wikimedia and VideoLAN. He has led teams and shipping efforts at CM.com—driving integrations, real‑time dashboards and cloud infrastructure on Azure—and previously shaped mobile platforms and security practices as a senior architect at Service2Media. Technically versatile, he spans front-end work (Angular, Vue, Ace editor contributions) to backend fixes in large open-source projects like MediaWiki, where he resolved media parsing and format issues and improved modularity. Comfortable across PHP, JavaScript, .NET and mobile stacks, he combines hands‑on coding with architectural thinking and a practical focus on accessibility, i18n and media support. A pragmatic problem solver, he often focuses on subtle compatibility and interoperability fixes—examples include IE7 comma bugs and CORS in web workers—that quietly improve developer and user experience.

23 years of coding experience

22 years of employment as a software developer

Computer Science, Computer Science at University of Twente

Ubbo Emmius

English, Dutch, German

Github Skills (13)

compatible10

mime10

php10

jpeg10

javascript10

ace-editor10

mediawiki10

browser-support10

webm9

webworker9

cors9

html7

css5

Programming languages (26)

C#CGoJSONHTMLTypeScriptShellAdblock Filter List

Github contributions (5)

wikimedia/mediawiki

Feb 2012 - Jan 2023

🌻 The collaborative editing software that runs Wikipedia. Mirror from https://gerrit.wikimedia.org/g/mediawiki/core. See https://mediawiki.org/wiki/Developer_access for contributing.

Role in this project:

Back-end Developer

Contributions:260 commits, 1 comment in 11 years

Contributions summary:Derk-jan primarily contributed to improving the MediaWiki software by addressing bugs and enhancing existing functionalities. Their work included fixing XMP parser errors related to JPEG files, implementing JPEG2000 MIME type fixes, and adding the ability to handle WebM files with AV1 and/or nullbyte terminated VP8/9. Additionally, they worked on splitting and combining classes to improve modularity within the system.

collaborative-editingmediawikiphpwikiwikipedia

ajaxorg/ace

Dec 2013 - Jun 2014

Ace (Ajax.org Cloud9 Editor)

Role in this project:

Front-end Developer

Contributions:8 commits, 3 comments in 5 months

Contributions summary:Derk-jan primarily focused on improving the functionality and compatibility of the Ace editor, an in-browser code editor. They addressed compatibility issues with older browsers like Internet Explorer 7 by fixing trailing commas, a common source of errors. They also improved the editor's ability to handle Cross-Origin Resource Sharing (CORS) in the worker process. Additionally, the user made improvements to theme options and settings for more intuitive user interaction.

cloud9

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