Mobile and desktop are affected
At first glance, it seems that
-webkit-text-size-adjust controls only the auto-scaling of small text in mobile versions of WebKit. However, the
‑webkit‑text‑size‑adjust property affects more than just auto-scaling, and more than just mobile browsers.
On the desktop,
-webkit-text-size-adjust also dictates whether text will be resized when the browser zoom feature is used. That is, whether the text actually gets bigger when you press ⌘+. If you do this:
…then you’ve just disabled text resizing entirely. When you hit ⌘+, the images and layout will get bigger, but text will stubbornly remain the same size. This is almost never what you want.
Most sites not specifically designed for mobile first should be well served by the default setting:
If you are designing for mobile first, or you are trying to disable unwanted auto-enlargement of small text in mobile Safari, use this technique:1
100% value tells WebKit to disable the automatic behavior, but to still allow user-initiated zoom.