The invisible engines: JavaScript libraries that power today's internet

The backbone of the modern internet

JavaScript libraries have become the fundamental building blocks of modern web development. These collections of pre-written code handle common tasks like animations, form validation, or data visualization, and allow developers to focus on creating unique features rather than reinventing the wheel. Most libraries are open source and free to use, creating a collaborative ecosystem where developers worldwide contribute to and maintain these essential tools.

The widespread adoption of libraries has democratized web development in remarkable ways. Techniques that once required specialized knowledge can now be implemented with just a few lines of code, enabling developers of all skill levels to create sophisticated, interactive websites. In many ways, these libraries represent the collective wisdom of the developer community, packaged in a form that anyone can use.

Our data shows just how integral libraries have become to the web ecosystem. Across the 84.4 million websites where we detect JavaScript libraries, we've identified 245 unique libraries in active use. While this diversity demonstrates the rich ecosystem available to developers, Figure 1 reveals that the most popular players are well established with jQuery leading at 14%, followed by core-js at 9.1% and Swiper at 6.9%.

This concentration at the top represents millions of websites relying on a relatively small set of trusted, battle-tested tools. The long tail of specialized libraries reflects how developers increasingly seek purpose-built solutions for specific requirements rather than one-size-fits-all approaches.

jQuery: the library that shaped the web

Despite being released in 2006—making it ancient, by web technology standards—jQuery continues to demonstrate remarkable staying power, running approximately 67.4 million websites. This versatile library simplifies webpage element manipulation, event handling, animations, and data loading without page refreshes through a concise, easy-to-use syntax that transforms how developers write JavaScript.

jQuery's mission was simple, yet revolutionary: “write less, do more.” It achieved this by abstracting away the complexities of cross-browser compatibility issues that plagued web development in the 2000s. While modern browsers have since standardized many features, jQuery's intuitive API and vast ecosystem of plugins continue to make it an attractive option for developers at all skill levels.

Looking at Figure 2, we can see jQuery's evolution over time. The significant jump in detected instances around August 2024 reflects improvements in our detection methodology rather than a sudden increase in adoption. Since then, jQuery has maintained a stable presence of approximately 67–68 million websites, showing its enduring relevance despite the emergence of newer alternatives.

Several factors explain jQuery's continued dominance:

• Legacy support: A vast number of existing websites built with jQuery remain in production, and the cost of refactoring to newer technologies often outweighs the benefits.
• Simplicity: jQuery's straightforward API makes it accessible to developers at all skill levels, from beginners to experts.
• Browser compatibility: While modern browsers have standardized many features, jQuery still offers a consistent interface across different environments.
• Extensive ecosystem: The library comes with a rich ecosystem of plugins and extensions that extend its functionality.

This persistence challenges the common narrative that developers must always adopt the newest technologies. As our data demonstrates, tried-and-tested solutions typically continue to provide value long after newer alternatives emerge.

Beyond the top 10: a specialized layer

Beyond the dominant libraries, a diverse array of specialized tools constitutes the next tier of JavaScript's development framework. Figure 3 highlights the libraries that are ranked 10–30 and fall under the ‘other’ category of the previous figure. Ultimately, it reveals interesting patterns in how developers address specific needs.

This second tier of top libraries reveals how specialized needs drive library adoption. jQuery UI (1.6%) extends jQuery's core functionality, while GSAP (1.5%) powers sophisticated animations. Performance optimization appears with LazySizes (1.3%), while Axios (1.2%) has become a standard for handling HTTP requests. The presence of MooTools (1.2%)—another legacy library released in 2006—further confirms that established solutions retain significant market share.

Notable in this list is React at position 22 (1.1%), a component-based library released by Facebook in 2013 that helps developers build interactive user interfaces. Utility libraries like Underscore.js (1.1%) and Lodash (1.1%) remain popular for data manipulation tasks, despite significant overlap in functionality. This diversity of specialized tools demonstrates the maturity of the JavaScript ecosystem.

Modern front-end frameworks: a growing presence

While traditional Document Object Model (DOM) manipulation libraries remain prominent, modern JavaScript frameworks designed for building complex user interfaces continue to gain traction. React appears at position 22 in our rankings with a 1.1% share (approximately 5.4 million websites), making it the most widely adopted modern framework in our data.

The relatively modest share of React compared to jQuery might seem surprising given its outsized presence in developer discussions and job postings. However, this disparity highlights an important distinction: while developers frequently discuss and learn these tools, their actual implementation across the broader web happens more gradually. Many websites simply don't require the complexity and overhead that comes with a full-featured framework.

The shift toward performance optimization

A notable trend in our data is the growing adoption of performance-focused libraries. LazySizes (1.3%, approximately 6.1 million websites) has become increasingly popular as developers prioritize page speed and performance metrics.

This trend aligns with broader industry shifts toward performance optimization, driven by both user expectations for instantaneous experiences and search engine algorithms that favor faster-loading websites.

JavaScript Cookie (0.9%) represents another specialized utility that helps developers manage browser cookies efficiently, addressing both performance and user privacy concerns.

Visualization and interactive content

Data visualization continues to be a significant use case for JavaScript libraries. Among the libraries in our second tier, GSAP (1.5%) stands out for enabling sophisticated animations and interactive content.

The presence of image-focused libraries like jQuery imagesLoaded (1.3%), PhotoSwipe (1.0%), Slick (1.0%), and Owl Carousel 2 (0.9%) demonstrates the continued importance of media handling in modern web experiences. These libraries help create engaging visual experiences while managing performance concerns around image loading and display.

Specialized tools for specific needs

Beyond the major categories, our data reveals specialized libraries serving specific niches within the top 30:

• Form enhancements: Libraries like Typeahead.js (1.2%) improve standard form elements with features like autocomplete functionality.
• File handling: Dropzone (1.3%) provides drag-and-drop file upload capabilities with preview functionality.
• Animation tools: Animate.css (1.2%) offers easy-to-implement CSS animations.
• Template handling: Handlebars.js (1.0%) remains a popular choice for client-side templating.
• Data management: PubSubJS (1.1%) facilitates communication between different parts of an application.

This specialization trend reflects the maturing JavaScript ecosystem, where developers increasingly seek purpose-built tools for specific requirements rather than one-size-fits-all solutions. The presence of Glide.js (1.4%), focused on creating lightweight slider components, further illustrates how developers gravitate toward specialized tools that solve particular UI challenges efficiently.

The future of JavaScript libraries

The JavaScript library landscape is in constant evolution. Performance optimization is becoming increasingly vital, with specialized tools gaining traction as page speed becomes a critical success factor. Meanwhile, the universe of specialized libraries continues to expand, addressing niche needs from cryptography to accessibility.

What's fascinating is the balance between innovation and stability. While new frameworks regularly emerge, established solutions like jQuery demonstrate remarkable staying power—reflecting the genuine value these tools continue to provide in addressing fundamental web development challenges.

JavaScript libraries represent a beautiful example of collaborative achievement: collective knowledge refined into practical tools that extend what's possible on the web. The internet of 2025 stands as a testament to this collaborative spirit—a tapestry of shared solutions pushing the boundaries of what's possible in the browser, enabling more powerful, efficient, and engaging digital experiences for everyone.