jQuery Never Dies, Even When It Should
Cloudflare helps operate CDNJS, the popular open-source content delivery network for frontend libraries. By analyzing anonymized request data from CDNJS with the team’s permission, we can observe real-world adoption patterns for JavaScript libraries. One question drives this analysis: once a site installs a library, does it ever move to a newer version?
Start with jQuery, the most widely used JavaScript library. The chart below shows CDNJS requests for a selection of jQuery versions over the last 12 months:
Occasional spikes, like the one for version 3.3.1, occur when very large sites add or remove CDNJS script tags. Version 3.4.1, released on May 2, 2019, shows a steady climb in requests. But the demand for older versions does not drop in response — version 3.2.1 averages 36M requests per day early in the sample, falling to 29M by the year’s end, a decline of roughly 20%. This matches a body of research indicating the average website lives two to four years. What stands out is that old jQuery versions never see a sharper decline tied to new releases; the growth of 3.4.1, popular as it is, does not alter the deprecation trend for its predecessors.
The oldest jQuery version CDNJS hosts is 1.10.0, released May 25, 2013. It still receives about 100k requests daily — and the sites using it are gaining popularity:
To verify this pattern isn’t unique to jQuery, look at another project — TweenMax:
TweenMax data has been smoothed with a one-week trailing average since its request volume is lower than jQuery’s. Version 1.20.4 begins the year at 18M daily requests and ends it at 14M, roughly a 23% decline, in line with the natural loss of websites. Meanwhile, version 2.1.3 climbs to 29M daily requests; the trend for older versions stays flat, offering clear evidence that releasing a new version has almost no influence on the fate of older ones.
This suggests a pragmatic conclusion: a library you publish today will live on websites indefinitely. For the web platform to keep supporting the breadth of existing sites, it must accommodate aged conventions indefinitely. At Cloudflare, we are exploring how to contribute to a more up-to-date web — and we invite your suggestions.
