The browser is running code that refers to $ before a usable jQuery reference is available. Check that jQuery loaded, then make sure it runs before scripts that depend on it. If another library uses $, switch to jQuery or a separate alias.
What “jQuery $ is not defined” means
$ is jQuery’s shorthand alias, but it is not guaranteed to mean jQuery everywhere: another library can use the same name, or the alias may not be available in the code’s scope. The error text alone does not reveal which cause applies. Start with the first failing line and the jQuery script request rather than assuming that script order is always the problem.
Use the browser’s developer tools to check the Console and Network panels. Find the first error, then locate the jQuery request and inspect its URL, response, and status. A missing, mistyped, failed, or blocked script can leave dependent code without jQuery’s global names; a blocked script fires an error event. See MDN’s script element reference.
Fix script loading and execution order
Verify that the page loads the intended jQuery file
Inspect the rendered page’s script elements, not just the source template. Confirm the jQuery URL is correct and that the request succeeds. If it is missing or failing, correct the URL or delivery problem and verify the request in Network before changing dependent code.
#1 Best Overall
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Load jQuery before plugins and application code
A plugin or app file that calls $ during evaluation needs jQuery to have run first. For ordinary classic scripts without async or defer, execution follows document parsing order. If jQuery appears after the script that uses it, put jQuery first.
Do not use async for scripts with dependencies
async scripts execute as soon as they are available, so their execution order is not guaranteed. Remove async from scripts that depend on one another, or manage their dependencies explicitly.
Rank #2
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- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
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Use defer in document order for classic external scripts
For classic external scripts, defer runs scripts after parsing while preserving the order of the script elements. Put jQuery before its plugin and app files, and use defer on each dependent script:
<script defer src="/js/jquery.min.js"></script>
<script defer src="/js/plugin-that-needs-jquery.js"></script>
<script defer src="/js/app.js"></script>This only works if the URLs load the intended files and the plugin and app are compatible with that jQuery version. This guidance is for classic scripts: module scripts defer by default, and defer has no effect on them. Check the script type before changing attributes. MDN documents the loading behavior in its script element reference.
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Resolve a conflict over the $ name
If jQuery is available but $ belongs to another library—or is unavailable in the relevant scope—use the full jQuery name or create a dedicated alias after jQuery loads. The jQuery API describes noConflict() as relinquishing jQuery’s control of $; it returns the jQuery object so you can keep using it under another name.
<script src="/js/jquery.min.js"></script>
<script>
var $j = jQuery.noConflict();
$j(function () {
$j(".notice").addClass("ready");
});
</script>Use the alias consistently in the code that relies on jQuery. The call must happen after jQuery loads and before that code uses the alias. See the jQuery.noConflict() API documentation and the jQuery Learning Center’s guide to avoiding conflicts with other libraries.
Rank #4
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Match the fix to what you find
| What you find | Likely explanation | What to do |
|---|---|---|
| The jQuery request is missing, failed, blocked, or points to the wrong file | jQuery did not become available. | Correct the URL or delivery, then verify the request succeeds. |
| jQuery appears after a plugin or app script | The dependency order is reversed. | Put jQuery first and keep that order if using deferred scripts. |
Related scripts use async |
They may execute in an unexpected order. | Remove async for dependent scripts, or use ordered defer for classic scripts or a dependency manager. |
jQuery exists, but $ resolves to another library or is unavailable in the failing code |
A name conflict or scope difference may be involved. | Use jQuery or set up a noConflict() alias after jQuery loads. |
| The error appears only in one bundle, callback, or interaction | The identifier’s scope or execution timing may differ there. | Inspect the exact failing line and execution context to see which names are available. A particular app’s scope cannot be diagnosed from the error text alone. |
Retest the failing behavior
Reload the page and repeat the interaction that originally failed. Confirm that the feature works, not merely that the console error has disappeared. Avoid adding a second jQuery copy as a guess: jQuery advises against loading two versions, and noConflict(true) has additional behavior documented in the API reference.
DOM readiness and jQuery availability are separate. A ready handler can wait until the DOM is ready, but it cannot repair a failed download or an execution-order race.
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