About Henri Sivonen

Photo of Henri Sivonen’s faceI am a software developer based in Helsinki, Finland. I work for Mozilla. (Note that since Open Source work often involves publishing personal opinions about work topics, you should not consider anything on this site as a position of Mozilla even if it carries Mozilla’s copyright notice.)

I mainly work on stuff above networking and below layout. Notably I’m the principal author and module owner of Firefox’s HTML parser, character encoding converters, and encoding detector. I am also a peer of the DOM and UA string modules. I’ve partipated at the WHATWG since 2004. As of October 2021, I’m primarily working on implementing an ECMA-402-scoped CLDR-compliant collator for ICU4X.

Previously, I worked on focus management in the context of out-of-process iframes. Earlier on, I developed an HTML5 validator and represented Mozilla on the HTML Working Group of the W3C.

In 2007, I graduated as Master of Science (Technology) from Helsinki University of Technology, Department of Computer Science and Engineering. I wrote my master’s thesis about HTML5 validation.

Contact Info

My personal email address is hsivonen@hsivonen.fi. Previously, I have used the email address hsivonen@iki.fi, which remains forwarded to hsivonen@hsivonen.fi. My work email is hsivonen@mozilla.com.

Finding Me on Various Services

FacebookI am not on Facebook
Google Docshsivonen@gmail.com (personal), hsivonen@mozilla.com (work), hsivonen@unicode.org (Unicode)

I have a separate page for cryptographic keys.