Deep inside his icy cave, the wise and powerful Yeti heard people asking, "Where did Zepto go?" Back when Foundation 4 was being conceived we switched to Zepto (with a jQuery option) for its smaller file size and faster load time.
Maintaining different code bases wasn't easy for us, either. For example, Zepto lacks a proper height calculation function, making certain grid calculations difficult.
To solve all this, the answer was clear as a spring Himalayan sky: Foundation 5 uses jQuery 2. In addition to better speed and industry acceptance, jQuery 2 benefits from better documentation and support as well. jQuery is API compatible.
But we assumed Zepto would be faster than jQuery. We didn't want to make the same assumption twice, so we tested Zepto vs. jQuery 2. The result: jQuery 2 has more operations per second. That gives Foundation 5 better performance, which translates to better experience for all users.
In the end, we want to help people design great products faster — and this time, that means giving the most responsive front-end framework in the world itself a speed boost.