How to Fix “Uncaught TypeError: Cannot read property ‘msie’ of undefined jQuery”

Learn how to fix the 'Uncaught TypeError: Cannot read property ‘msie’ of undefined jQuery' error in older jQuery versions. Follow this guide for a quick and effective solution

You updated jQuery, and now the console is screaming: “Uncaught TypeError: Cannot read property ‘msie’ of undefined.” A slider stops sliding, a menu goes dead, and nothing in your own code mentions msie. So where’s it coming from?

Some old script (a theme, a plugin, or a snippet you inherited) is still calling jQuery.browser.msie. That jQuery.browser object was deprecated back in jQuery 1.3 and removed for good in jQuery 1.9. Once it’s gone, jQuery.browser is undefined, and reading .msie off undefined throws the TypeError. That’s the whole story: you asked for a property on something that no longer exists.

Here’s a quick stopgap that puts the object back, so the old code stops choking:

/**
 * Fix for the 'msie' property error in older versions of jQuery.
 * This snippet initializes the jQuery.browser object to avoid
 * 'msie' related errors.
 *
 * @namespace jQuery.browser
 * @property {boolean} msie - Indicates if the browser is Internet Explorer.
 * @property {number} version - Stores the version of Internet Explorer.
 */
jQuery.browser = {};

(function () {
    // Initialize the msie property as false and version as 0
    jQuery.browser.msie = false;
    jQuery.browser.version = 0;

    // Check if the user agent string contains 'MSIE' and extract the version number
    if (navigator.userAgent.match(/MSIE ([0-9]+)\./)) {
        jQuery.browser.msie = true;
        jQuery.browser.version = RegExp.$1;
    }
})();

Load that before the script that’s failing, and the error goes quiet.

What the snippet does

1. Rebuilds the object: sets jQuery.browser back to an empty object so nothing reads .msie off undefined.
2. Sets safe defaults: an IIFE marks msie as false and version as 0.
3. Sniffs the user agent: if navigator.userAgent matches MSIE, it flips msie to true and pulls the version number out.

Be honest about what this is

This is a patch, not a fix. It brings back a feature jQuery deliberately dropped, and user-agent sniffing is unreliable (real Internet Explorer is effectively dead, and Edge retired the IE engine). You’re keeping legacy code alive, not modernizing it.

If you want the safe, supported version of this same idea, load the official jQuery Migrate plugin. It restores jQuery.browser and other removed APIs, and it logs warnings telling you exactly which lines to clean up.

The real fix, when you have time

The right move is to stop calling jQuery.browser at all. Track down the script throwing the error (the browser console will name the file and line), update the plugin or theme that ships it, or swap the check for feature detection. If you just need to guard a single access, optional chaining does it in one line: jQuery.browser?.msie returns undefined instead of throwing.

Compatibility

The shim above is meant for old jQuery-dependent code that still expects jQuery.browser. On a current jQuery build with no legacy callers, you don’t need it at all. When you’re ready to do this properly, reach for feature detection (Modernizr, or a plain capability check) instead of asking which browser someone is running.