Browserslist Defaults §

You can pick a sound set of versions with the defaults query, which was thoroughly designed by the Browserslist community. It helps promote best practices and avoid common pitfalls.

"browserslist": [
  "defaults"
]

Explanation of defaults §

The defaults query is a shortcut for:

"browserslist": [
  "> 0.5%", 
  "last 2 versions", 
  "Firefox ESR", 
  "not dead"
]

List item relationship §

You can combine versions matched by multiple queries with or or ,. you can intersect them with and. So the following is the same as above:

"browserslist": [
  "> 0.5%, last 2 versions, Firefox ESR, not dead"
]
 
// or
"browserslist": [
  "> 0.5% or last 2 versions or Firefox ESR and not dead"
]

> 0.5% §

It will include all browser versions with > 0.5% of the audience worldwide. So if 0.5% of users globally still use a certain version of the browser, that version of browser will be included.

last 2 versions §

It will include only the last 2 versions of the browser.

Firefox ESR §

It will include Firefox Extended Support Release which is updated roughly annually.

not dead §

You can also negate any query with not if it’s not the first one in your list. A query with not can’t be the left-hand one in the list. A query with not is always joined to the left-hand one with and, even if or or , are used.

The “dead” browsers mainly includes IE, but also includes other minor browsers like Blackberry Browser, Opera Mobile, etc.