Download websites that use jQuery Migrate

About jQuery Migrate

jQuery Migrate is the only entry in this index whose presence is a diagnosis rather than a decision. It exists to keep code written against an older interface working against a newer one, which means nobody adds it because they want it. It arrives because something old is still in the building and removing it would have cost more than shimming it.

As of September 2026 we detect it on 16,872,549 sites, and every one of those is a site where that trade was made and never revisited. The library was always meant to be temporary. At this scale, temporary has clearly become permanent for a very large population.

That makes it one of the sharpest maintenance signals available. A site carrying it has, by definition, front-end code old enough to break against a current release, and the presence of the shim means nobody has done the work to fix the underlying calls. Compared to inferring age from design or copyright dates, this is direct evidence rather than a guess.

The most common release we see is 3.4.1, which is itself informative, because the shim is versioned alongside the library it patches. A site running an old shim against an old library is a different proposition from one running a current shim during an active migration, and the pair of versions distinguishes them.

The commercial use is straightforward and slightly uncomfortable. This population is a list of properties carrying technical debt that the owners have chosen not to pay down. For agencies selling rebuilds, for security vendors scoping legacy exposure and for acquirers assessing what they are buying, that is precisely the list they want and precisely the list that does not exist publicly.

United States accounts for 6,249,592 of detections and the .com zone leads, both following the age profile of those markets rather than anything about the library.

Because the signal is only meaningful in combination, the export carries every detection on a domain on one row: the shim, the library version it is patching, the platform above them, the interpreter below and the hosting underneath. Filtering that stack locally is how a maintenance hypothesis becomes a qualified list.

There is an important asymmetry in how this signal should be used. Its presence is strong evidence of legacy code. Its absence proves nothing, because a site may have removed the shim while leaving the underlying problem in place, or may never have needed it despite being equally old. Treating absence as evidence of modernity will produce a cleaner-looking dataset and a worse one.

The population also has a useful internal structure. Sites cluster around the theme and plugin combinations that bundled the shim, so grouping by the surrounding stack tends to surface whole families of properties built from the same starting point, frequently by the same agency. Those families are more valuable than individual rows, because a pitch that works for one member usually works for the rest.

It is published by the OpenJS Foundation under the MIT license and has existed since 2013. The project has always been explicit that it is a bridge rather than a destination, which makes its footprint a reasonable measure of how much of the web is still standing on the bridge.