Web Almanac reveals shifting web performance trends

The 2024 edition of the Web Almanac paints one of the clearest pictures yet of how web performance is changing in the real world. Drawing on Chrome UX Report (CrUX), WebPageTest, and Lighthouse data for roughly 16.9 million sites and 83 TB of crawls, it goes beyond synthetic benchmarks to show how fast, or slow, the web actually feels for users. The results are encouraging, but they also reveal new performance fault lines.

Core Web Vitals (CWV) are improving across the board, and more than half of the web finally meets Google’s “good” thresholds. Yet mobile users, low‑end devices, and JavaScript‑heavy architectures are increasingly left behind. Media usage and page weight keep climbing, while the shift from First Input Delay (FID) to Interaction to Next Paint (INP) is forcing developers to confront responsiveness problems that used to hide under the surface.

Core Web Vitals: Global gains, uneven progress

Core Web Vitals remain the central lens through which the Web Almanac evaluates user‑perceived performance. In 2024, around 56.3% of websites meet all three CWV thresholds in field data, a sharp rise from roughly 40% in 2022. This continues a multi‑year trend of steady improvement since the metrics were first introduced, confirming that optimization work is paying off globally.

The SEO chapter reports that 48% of mobile experiences and 54% of desktop experiences now pass all three vitals, Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). That is a substantial jump from 39% mobile and 43% desktop in 2022, and a remarkable leap from just 20% of mobile experiences passing CWV in 2020. These gains show that developers, frameworks, and platforms are gradually embracing performance as a first‑class concern.

Yet “more than half” also means nearly half of real users are still encountering sub‑optimal experiences. Many of these failures are concentrated in specific problem areas: slow content rendering on JavaScript‑heavy sites, interactivity issues on less powerful devices, and pages overloaded with images, video, and third‑party scripts. The story of 2024 is not that CWV is solved, but that baseline expectations are rising and laggards now stand out more clearly.

INP replaces FID: A harsher, more realistic interactivity metric

One of the most consequential changes highlighted by the Web Almanac is the March 12, 2024 replacement of First Input Delay (FID) with Interaction to Next Paint (INP) as the interactivity Core Web Vital. FID only measured the delay for the first input in a session, which meant that once a page’s initial event loop was unblocked, ongoing responsiveness problems could be missed entirely. INP instead considers the latency of all user interactions across a visit and reports a representative value, offering a much more realistic view of responsiveness.

This change has exposed weaknesses in JavaScript‑heavy architectures and single‑page applications (SPAs). The Performance and SEO chapters note that many sites saw their CWV pass rates drop as INP took over, even if they had looked healthy under FID. Long task chains, heavy client‑side routing, and complex component trees that were previously masked by FID’s narrow focus are now reflected in worse INP scores and lower pass rates.

The shift to INP is already influencing how teams prioritize work. Instead of only optimizing the initial load, developers must now consider the entire lifecycle of user interaction: event handlers, state updates, re‑renders, and background JavaScript tasks. Techniques like splitting long tasks, deferring non‑critical work, and reducing client‑side complexity are no longer optional optimizations, they are necessary steps to maintain good CWV scores and avoid regressions in responsiveness.

Desktop vs mobile: The widening performance inequality gap

Despite global improvements, the Web Almanac underscores a growing “performance inequality” gap between high‑end and low‑end devices, echoing Alex Russell’s research on this topic. While desktop devices increasingly provide fast, responsive experiences, many mobile users, particularly on lower‑end hardware and constrained networks, see only partial benefits from the broader CWV gains.

In 2024, 54% of desktop experiences pass all three Core Web Vitals, versus 48% on mobile. The disparity is especially stark for interactivity: desktop INP pass rates hit an impressive 97%, but mobile lags at 74%. In other words, almost every desktop session appears responsive by CWV standards, while roughly one in four mobile sessions still encounters noticeable interactivity issues.

This gap is not just a matter of network conditions. Modern web apps frequently push large JavaScript bundles, complex frameworks, and heavy media to all devices equally, without adequate adaptation for weaker CPUs and memory constraints. Even as performance culture improves, design and implementation choices often assume desktop‑class capabilities by default. The result is a web where aggregate metrics look better every year, yet the users who can least afford poor performance remain disproportionately impacted.

LCP, lazy‑loading, and the pitfalls of heavy client‑side rendering

Largest Contentful Paint continues to be one of the hardest Core Web Vitals to optimize, and the Web Almanac surfaces several recurring anti‑patterns. On mobile in 2024, 59% of experiences pass LCP, compared to 72% on desktop. One consistent culprit is improper lazy‑loading of key content, especially the main hero image that typically becomes the LCP element.

The Performance chapter finds that 16% of mobile pages still lazy‑load their LCP image, either via the native loading="lazy" attribute or custom JavaScript. This is only a modest improvement from 18% in 2022. While custom lazy‑loading approaches dropped from 8.8% to 6.7%, native lazy‑loading of LCP images remains stubbornly common, barely changing from 9.8% to 9.5%. For these sites, the browser is told to deprioritize the very element that defines perceived load speed, delaying LCP unnecessarily.

Beyond lazy‑loading, the Web Almanac shows a strong correlation between extreme client‑side rendering and poor LCP outcomes. As long as client‑side generated content stays below around 70% of the page on mobile, the share of pages with good LCP hovers near 60%. Once client‑side generated content exceeds 70%, the proportion of good LCP pages drops steeply to about 40%. Heavy client‑side rendering, where most of the meaningful content appears only after JavaScript executes, remains a fundamental performance anti‑pattern even in 2024.

Visual stability: Better CLS, but costly animations persist

On the positive side, visual stability continues to improve. Cumulative Layout Shift (CLS) pass rates now reach 79% on mobile and 72% on desktop. These gains reflect widespread adoption of basic best practices such as reserving space for images and embeds, avoiding sudden content injections above existing content, and stabilizing dynamic UI elements. Users increasingly experience fewer jarring jumps as content loads.

However, the Web Almanac notes that non‑composited animations remain prevalent and are even slightly more common than in 2022. About 39% of mobile pages and 42% of desktop pages use animations that trigger layout and paint work rather than relying solely on compositor‑friendly properties like transform and opacity. These rates are up marginally from 38% and 41% in 2022, suggesting that visual polish is still frequently implemented in ways that burden the main thread.

While CLS itself does not directly penalize non‑composited animations, these effects can contribute to jank, frame drops, and interaction delays, issues that INP is more likely to expose. As sites layer on more micro‑interactions and complex transitions, the challenge is to keep them “cheap” by using performant properties and respecting the limits of the main thread, particularly on low‑end mobile devices.

Media and formats: More images, more video, and heavier pages

The Media and Sustainability chapters make clear that media is still one of the main drivers of page weight. In 2024, 99.9% of pages request at least one image, and both image dimensions and total pixel counts keep rising. Even though compression techniques have improved and modern formats are more widely adopted, total image bytes continue to trend upward, adding pressure to LCP and overall load times.

Video usage is also climbing quickly. Between 2022 and 2024, video adoption on the web rose by 32%, bringing rich storytelling and engagement opportunities, but also greater bandwidth and performance demands, especially on mobile networks and in emerging markets. Poorly optimized video can dominate page weight, slow initial renders, and degrade responsiveness as players and tracking scripts load.

On the format front, the Web Almanac highlights a substantial surge in modern image formats. WebP usage grew by 34% between 2022 and 2024, and AVIF adoption skyrocketed by 386%. Yet AVIF still accounts for only about 1.4% of desktop and 1.05% of mobile image formats; JPEG remains deeply entrenched. The result is a tension: developers are moving to more efficient formats, but not fast enough, and not consistently enough, to offset the growth in both the number and size of images. The long‑term trend in page weight is still upward.

Page weight and Core Web Vitals: A nuanced relationship

The 2024 Page Weight chapter reinforces that Core Web Vitals are intentionally “human‑centric” metrics. They measure what users feel, how soon they see meaningful content, how quickly the interface responds, how stable the layout is, rather than simply counting bytes. While heavier pages generally correlate with worse LCP and INP, there are notable exceptions where large sites still achieve good scores through careful prioritization.

These exceptions usually rely on a combination of strategies: delivering critical content early in the HTML, using CDNs and smart caching, splitting and deferring non‑critical JavaScript, and aggressively optimizing above‑the‑fold media. In such architectures, even if the total page weight is high, the portions that matter most to early user perception are streamlined and scheduled intelligently.

Nevertheless, multi‑year data from the HTTP Archive shows a continued drift toward larger JavaScript bundles and heavier pages overall. The Web Almanac therefore reiterates familiar but still vital guidance: reduce unused JavaScript, trim third‑party bloat, compress and resize images appropriately, and avoid shipping non‑essential assets on first load. For many sites, especially those already following best practices for HTML and resource prioritization, these are the main remaining levers for further CWV gains.

Platforms, CMSs, and ecommerce: Performance as ecosystem competition

Another key theme in the 2024 Web Almanac is the central role of platforms, particularly CMSs and ecommerce solutions, in shaping web performance. As of June 2024, around 51% of sites in both the desktop and mobile datasets are powered by a CMS, up from 48% on mobile in 2022. This means that a majority of real‑world user experiences are effectively mediated by a relatively small set of platforms and ecosystems.

Despite INP raising the bar for interactivity, many major CMSs manage mobile INP pass rates of roughly 80% or higher, demonstrating that good performance can be baked into templates, themes, and default configurations. At the same time, laggards such as Tilda and 1C‑Bitrix still fall short of the global INP pass rate of around 84.1%, exposing disparities within the CMS landscape. For site owners, platform choice can thus be a decisive factor in whether their pages meet CWV thresholds without extensive custom tuning.

The Ecommerce chapter further connects performance to business outcomes. It reports the share of storefronts on major ecommerce platforms that achieve “good” scores across LCP, INP, and CLS, and emphasizes that better Core Web Vitals are linked to SEO advantages and higher conversion rates. While leading platforms have generally improved their CWV pass rates year‑over‑year, a significant subset of storefronts on each platform still fails at least one metric. In an increasingly competitive market, performance is becoming not just a technical concern but a differentiator baked into product and platform strategy.

The 2024 Web Almanac shows that the web is getting faster, more responsive, and more stable than it was in 2020 or even 2022. A majority of sites now pass Core Web Vitals, modern image formats and better compression are more common, and CLS regressions are less frequent. The adoption of INP as a Core Web Vital has sharpened the industry’s focus on real interactivity, encouraging developers to treat responsiveness as a continuous property rather than a one‑time hurdle at initial load.

At the same time, the report underscores that progress is uneven. Mobile users, low‑end devices, JavaScript‑heavy architectures, and media‑rich experiences still face significant challenges. Page weight and JavaScript volume continue to climb, lazy‑loading and client‑side rendering anti‑patterns remain widespread, and non‑composited animations tax the main thread. As CMSs and ecommerce platforms shape more of the web, performance is increasingly an ecosystem issue as much as an individual site concern. The next phase of web performance work will be less about discovering what matters, Core Web Vitals have made that clear, and more about closing the gap between best practices and everyday implementation across the full diversity of devices, networks, and platforms.