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I'm Tantek Çelik, Mozilla Web Standards Lead, developing and coordinating Mozilla work on web standards

I'm based in San Francisco.


Mozilla offices I visit in rough order of frequency

  • Berlin - ~once a year
  • Toronto - have visited once for a CSS Working Group meeting, would like to visit again!

want to visit

Our co-working spaces I'd like to visit:

past offices

Past offices I have visited:



User pages of Mozilla folks I've worked / am working with:

Additional Mozillians I'm working with:


Ali Spivak, Anne van Kesteren, Arthur Edelstein, Arun Ranganathan, Austin King, Aza Raskin, Boris Zbarsky, Brian Birtles, Chenxia Liu, Cameron McCormack, Cathleen Berger, Chris Blizzard, Chris Riley, Dan Mills, David Baron, David Bryant, Dietrich Ayala, Ellen Spertus, Emily Kager, Eric Rescorla, Fantasai, Gordon Brander, Gregor Wagner, Irakli Gozalishvili, J.C. Jones, Jen Simmons, Jet Villegas, Joe Hildebrand, Johnny Stenback, Jonas Sicking, Josephine Lau, Josh Carpenter, Karl Dubost, Michael Hanson, Michelle Thorne, Mike Hoye, Miriam Avery, Nicole Shadowen, Peter Saint-Andre, Robert O'Callahan, Rosana Ardila, Sean Voisen, Sean White, Simon Sapin, Xidorn Quan, Zbigniew Braniecki


I’ve been participating in web standards for over twenty years, beginning with leading the implementation of the Tasman rendering engine in Internet Explorer 5 for Macintosh.

I’ve written and edited many Cascading Style Sheets specifications (CSS 2.1 & many CSS3 modules), but also co-invented microformats, drove key features of vCard4 in the IETF, and been part of HTML5 and the HTML Living Standard work at WHATWG (authoring one of the first books and video tutorials on HTML5). From 2014-2018 I was co-chair of the W3C Social Web WG where I helped produce several W3C Recommendations in record time.

I recently served as an elected member of the W3C Advisory Board (2020-2022), helping drive a vision for a W3C based on shared values and community self-governance. During my previous tenure (2013-2018) I drove more openness and transparency in the processes of W3C as well as more liberal licensing of W3C standards.

I am particularly passionate about and actively involved in the IndieWeb movement -- standards, events, and community -- which you should definitely ask me about.

I hold Bachelor of Science and Master of Science degrees in Computer Science from Stanford, and 16 patents. I enjoy trail running, yoga, and bouldering. You can find out lots more about me and see active examples of my work on my blog at


  • 2013-07-01…2018-06-30 W3C Advisory Board
  • 2011-276 - present: Mozilla employee
  • 2010-146 - 2011-175: Mozilla contractor
  • before 2010-146: occasional Mozilla contributor (e.g. irc, wiki, bugzilla)

See Also