Last checked and updated on 09 Jun 2026
What Is New in jQuery 1 (summary table)
jQuery 1.12 focuses on compatibility, bug fixes, and aligning the codebase with jQuery 2.x, while maintaining support for older browsers like Internet Explorer 6-8.
| Category | Key Changes |
|---|---|
| New Features & Improvements | Added the .width(), .height(), and related methods returning fractional pixel values. Performance improvements in .css() and .animate(). |
| Bug Fixes | Numerous fixes, including issues with IE 11 in compatibility view, iframe events, and CSS animation handling in older Android browsers. |
| Alignment with jQuery 2.x | The 1.x and 2.x codebases were unified, sharing the same API. This makes maintaining both versions easier and ensures consistent behavior. |
| Deprecated Features Removed | Previously deprecated APIs like .andSelf() were finally removed (replaced by .addBack()). |
How does jQuery 1.12 handle CSS dimensions differently?
The core change is that dimension methods like .width() now return fractional pixel values when the browser supports it. Before, jQuery would round these values down.
In practice, this means your measurements are more precise. If an element is 100.5 pixels wide, .width() returns 100.5 instead of 100. This matters for modern, high-DPI displays and responsive layouts where sub-pixel accuracy can prevent cumulative layout errors.
The same logic applies to .height(), .innerWidth(), .innerHeight(), .outerWidth(), and .outerHeight(). The .css() and .animate() methods were also optimized to handle these fractional values more efficiently.
What were the major bug fixes for older browsers?
A significant batch of fixes targeted edge cases in Internet Explorer and other legacy environments. One notable fix resolved an issue where IE 11, when set to use compatibility view, could incorrectly report that it was supporting AJAX file uploads via iframes.
Other fixes tackled problems with event handling on removed iframes, which could cause errors, and corrected CSS animation behavior in the old Android Stock Browser (versions 4.0-4.3). These fixes solidify jQuery's claim of robust cross-browser support, even for the tricky, older ones.
Why was unifying the 1.x and 2.x codebases a big deal?
Prior to version 1.11 and 2.1, the 1.x (IE 6/7/8 compatible) and 2.x (IE 9+ only) codebases were developed separately. This was a maintenance burden and risked the two branches drifting apart in behavior.
The unification meant both versions now share the same core code module. The only difference is the support file that adds back compatibility for older Internet Explorer. For developers, this guarantees the API is identical. For the jQuery team, it means a bug fix in one branch is automatically a fix for the other, making development much more efficient.
FAQ
I'm on jQuery 1.9. Should I upgrade to 1.12?
Yes, absolutely. The 1.12 release includes years of bug fixes and performance improvements. The upgrade path from 1.9 is straightforward, but you should test for the removal of long-deprecated methods like .andSelf() which is now .addBack().
Does jQuery 1.12 work on modern mobile browsers?
Yes, it works well. Specific fixes were made for the old Android Stock Browser (4.0-4.3). For current versions of iOS Safari, Chrome, and others, compatibility is excellent, including the new fractional pixel support.
What happens if I use the removed .andSelf() method?
The method will simply not exist, causing a JavaScript error. You must replace all instances of .andSelf() with its modern alias, .addBack(), which has been available since jQuery 1.8.
Is the API exactly the same as jQuery 2.x now?
For all practical purposes, yes. The unification of the codebases ensures the public API is identical. The only differences are under-the-hood to support older IE in the 1.x line.
Are there any performance regressions in this release?
No, the opposite. Work was done to improve performance, particularly in the .css() and .animate() methods when dealing with fractional values. The code unification also reduces the chance of future bugs.