Flexbox browser support Three versions of the flexbox spec – each with different syntax – have been implemented in browsers. The two 2012 specs are roughly equivilant in terms of features, differing mainly in syntax. The earlier 2009 spec is less comprehensive though covers a lot of the same ground. Flexbox 2012 — W3C Candidate Recommendation, September 2012 Opera 12.1+, Firefox 22+. Chrome 21 -we