Font sizing best practice in 2014

Question

Decided to obtain a better working knowledge of font sizing best practice, read until my eyes bled, and find I continue to have questions. So much posted is old (older than few years) and change happens fast.
To the point; Since use of em units (or percentages) is often preferred, I now see that rems (root em) is another option, which leads me to ask:
Should I consider using “rem” sizing?… or, do browser zooming capabilities of modern browsers mean I do not have to obsess over how precise I must be in guesstimating how viewers actually see my written content as they have better control at their end? Is em compounding of sizes something that must be considered?
Thanks-

Answer 1

Use a mixture of what is best suited.
For document level I use pixels as in
/* Document level adjustments */
html {
  font-size: 13px;
@media (min-width: 760px) {
  html { font-size: 15px; }
@media (min-width: 900px) {
  html { font-size: 17px; }
Then for the modules I use root level ems as in
/* Modules will scale with document */
header {
  font-size: 1.5rem;
footer {
  font-size: 0.75rem;
aside {
  font-size: 0.85rem;
Then the size that will scale with the modules
/* Type will scale with modules */
h1 {
  font-size: 3em;
h2 {
  font-size: 2.5em;
h3 {
  font-size: 2em;
Using this method I keep each scenario under complete control.
A List Apart has a nice article on the subject.