jQuery .browser Property

What Is jQuery.browser?

jQuery.browser (alias $.browser) was a plain object of flags read from navigator.userAgent — browser class booleans plus $.browser.version for the rendering engine (added in jQuery 1.0 / 1.1.3).

$.browser          → { msie, mozilla, webkit, opera, … }
$.browser.version  → "engine version string"

// Typical legacy flags:
$.browser.msie
$.browser.mozilla
$.browser.webkit   // since 1.4
$.browser.opera
$.browser.safari   // deprecated flag

// Modern jQuery 1.9+ / 3.x:
typeof $.browser   → "undefined"  (unless Migrate)

How to Use jQuery.browser (Legacy)

Only for reading old code — do not add new UA sniffing.

1. Confirm you are on jQuery ≤ 1.8, or load jQuery Migrate with 1.9+.
2. Read a flag such as $.browser.webkit or $.browser.msie.
3. Optionally read $.browser.version for the engine version string.
4. Plan a rewrite: replace the branch with a real feature / capability check.

Pseudocode

// Legacy (removed in jQuery 1.9):
ua = navigator.userAgent
$.browser = parse flags from ua   // msie / mozilla / webkit / opera
$.browser.version = engine version string

if $.browser.webkit:
    // old browser-specific branch
else if $.browser.msie:
    // another branch

// Modern replacement idea:
if CSS.supports("display", "flex"):
    use flex layout
if typeof fetch === "function":
    use fetch API

Cheat Sheet

Keep these facts handy while reading legacy jQuery browser sniffing.

* safari flag was itself deprecated in favor of webkit.

Live Preview

This widget loads jQuery 1.12.4 so $.browser still exists. Pick a flag to inspect.

Loading jQuery 1.12.4…

jQuery Examples

Examples 1–3 use jQuery 1.12.4 so $.browser works. Example 4 shows the modern path with jQuery 3.x.

// Requires jQuery ≤ 1.8 or 1.12 + browser present
jQuery.each(jQuery.browser, function (i, val) {
  console.log(i + " : " + val);
});

webkit : true
version : …
mozilla : false
…

console.log($.browser.msie);     // true only on old IE UA
console.log($.browser.version);  // engine version string

if ($.browser.msie) {
  console.log("IE engine: " + $.browser.version);
}

false
…version string…

if ($.browser.webkit) {
  console.log("This is WebKit!");
} else {
  console.log("Not WebKit");
}

This is WebKit!
(or “Not WebKit” on non-WebKit UAs)

console.log(typeof $.browser);  // "undefined" in jQuery 3.x

var flex = window.CSS && CSS.supports("display", "flex");
var hasFetch = typeof fetch === "function";

console.log("flexbox: " + flex);
console.log("fetch: " + hasFetch);

undefined
flexbox: true
fetch: true

Performance Notes

Speed is not the problem — correctness is. Feature tests stay valid as browsers change; UA sniffing does not.

Key Takeaways