April’s cumulative update for Windows 11 24H2 landed at a manageable 1,287 MB. A month later, May’s package exploded to 4,369 MB. The culprit? A bonanza of AI-driven semantic search components bundled into the standard monthly servicing stack. The same update, when extracted, sprawled to nearly 9 GB. But before you panic about your bandwidth cap, know this: nearly every real-world PC downloads only a fraction of that monstrous catalog listing.

Microsoft’s Update Catalog presents the full, unvarnished package—the heavy master file designed to service any eligible machine, no matter how far behind on patches. Actual downloads, shaped by hardware applicability checks and differential delivery, usually run between 1.5 and 2 GB. In the worst-case test scenario—a fresh virtual machine with zero prior updates—the system pulled just 1.7 GB out of a 4 GB-plus catalog payload. Your personal device almost certainly downloads less.

The 30,000-foot view: why cumulative updates keep bloating

Windows 11 quality updates are cumulative by design. Each monthly Patch Tuesday release is a self‑contained capsule that carries not just the current month’s fixes, but every preceding fix needed to bring a system current. It’s a strategy that prioritizes reliability and simplicity: an admin can apply the latest LCU and know the machine is fully patched without chasing a chain of older packages.

The trade‑off is unbounded growth. As each update inherits more historical payloads, metadata, and binary differentials, the package swells. Microsoft attempted to tame this with Checkpoint Cumulative Updates, introduced alongside 24H2. Periodically, the company would nominate a particular update as a new baseline; subsequent updates would ship only the changes since that checkpoint, dramatically shrinking download sizes.

On paper, it worked. After a September 2024 checkpoint, 24H2 updates stayed relatively compact—often 200 to 500 MB early on, gradually creeping to the 1.3 GB range by April 2025. Then the May 2025 update arrived, and the checkpoint savings evaporated. The compressed .msu file jumped by roughly 3 GB, while the decompressed contents grew by 2.5 GB—an inversion that hints at already-compressed or compression-resistant payloads.

Inside the May 2025 spike: AI arrives in patch notes

A forensic dig by Windows Latest uncovered the smoking gun: dozens of new MSIX packages inside May’s update that were entirely absent in April. Their names read like a roll call of an on‑device AI stack:

  • PSTokenizer
  • Text Recognition Session
  • PSOnyxRuntime
  • Query Processor Session
  • Image Search Session

All are tied to Windows 11’s semantic search and on‑device intelligence features, built on the Onyx runtime Microsoft has released for developers. When you add up these payloads, they account for nearly the entire 3 GB delta. No single file stood out as a monster; rather, the increase came from a broad expansion of deeply integrated AI components.

Critically, these components are not downloaded or installed on every PC. Windows Update runs real‑time applicability checks—inspecting CPU, NPU, installed features, and patch history—before deciding which pieces to send. The semantic search MSIX files, initially developed for Copilot+ PCs with Snapdragon NPUs, simply won’t apply to a standard Intel desktop without a compatible neural engine. That’s why the fresh VM pulled 1.7 GB instead of 4.4 GB: the AI payloads were filtered out.

What this means for you, right now

If you’re at home

For most consumers, the monthly update download remains in the 1.5–2 GB range—a size that, while not trivial, fits easily into overnight idle time or a short background session. The catalog figure of 4 or 5 GB is a theoretical maximum for a device that needs every possible component. Yours almost certainly doesn’t.

You can verify this directly. Open Settings > Windows Update > Advanced options > Delivery Optimization > Activity monitor. The screen shows precisely how many megabytes came from Microsoft’s servers, from local PCs, and from your own cache during the last update cycle. If you’ve enabled peer‑to‑peer sharing or Delivery Optimization, the Microsoft‑sourced chunk might be even smaller.

If you’re an IT administrator

Enterprises feel the pain much more acutely. The full, uncut .msu package is what flows through WSUS, Configuration Manager, offline servicing tools, and distribution points. A single 4.4 GB update, multiplied by multiple architectures (x64, ARM64), multiple sites, and a chain of superseded updates, quickly bloats storage.

According to the Windows Latest analysis, the yearly storage cost per architecture, per distribution point, has leaped from roughly 11 GB (2024 cadence) to around 52 GB (2026 cadence). Across five distribution points and two architectures, that’s half a terabyte of disk consumed by monthly servicing alone—before you even count retained superseded updates or offline image maintenance.

Large packages also strain branch‑office bandwidth, lengthen replication windows, and inflate backup volumes. While Delivery Optimization and peer‑to‑peer caching lighten the load on endpoints, the upstream infrastructure still has to ingest, store, and distribute the full catalog package every month.

How we got here: a servicing model under pressure

Windows’ servicing philosophy was forged in an era before neural processing units and semantic search models became part of the operating system. The cumulative model and its checkpoint variant were designed for a patch landscape dominated by security fixes and core OS improvements—payloads that, while cumulative, grew at a slow, predictable pace.

What changed is the nature of the payload. On‑device AI features are not light tweaks; they bundle language models, tokenizers, runtimes, and specialized libraries. These assets are inherently large and often already compressed, making them resistant to the usual size‑reduction tricks. Worse, as hardware support expands from Snapdragon NPUs to Intel and AMD neural engines, multiple variants of the same component land inside the same master package, each gated by applicability rules but all occupying space in the catalog.

Apple’s macOS, often cited as a counterexample, enjoys a much tighter hardware ecosystem. Apple controls the entire stack and can drop support for old components aggressively, shipping only the delta that a handful of supported Macs require. Windows, by contrast, must service an ocean of hardware combinations—countless CPU generations, GPU drivers, firmware variants, and enterprise software environments. Microsoft’s commitment to backward compatibility and offline installability forces a monolithic package structure, even when intelligence at the delivery edge whittles the actual download.

What you can do about it

For home users:
- Check your real download size in the Delivery Optimization Activity monitor (path above).
- If you’re on a metered connection, set your network as “metered” in Settings > Network & Internet > Properties; Windows Update will then avoid large downloads until you approve them.
- Use Active Hours to ensure updates don’t surprise you during critical work.

For IT administrators:
- Audit your distribution point storage. Look for superseded updates that can be removed and ensure cleanup maintenance tasks are running on WSUS/ConfigMgr.
- Leverage Delivery Optimization peer‑to‑peer across your network to reduce WAN traffic, but recognize it doesn’t shrink the upstream package.
- Evaluate whether your organization truly needs to keep every architecture’s full catalog package online. If you don’t deploy ARM64 devices, prune that content.
- Pressure Microsoft through official channels (Feedback Hub, Microsoft 365 admin center) to separate AI feature payloads from mandatory security updates, or to issue more frequent checkpoints.
- For large update deployment, consider phased rings with careful monitoring of actual data transfer using tools like Windows Update for Business reports or third‑party bandwidth monitors.

Power users and tinkerers:
- You can inspect the composition of a downloaded .msu by extracting it with 7-Zip or using expand –F:* .msu folder. Compare the files against a previous month to spot new additions.
- Run Get-WindowsUpdateLog in PowerShell to see exactly what your system requested and downloaded.

Outlook: the month the meter started spinning faster

May 2025 may mark the moment when AI truly “shipped” inside Windows servicing, and the size trendline suggests it won’t retreat. Without a new checkpoint, cumulative updates will keep piling on more payload, and as on‑device AI features become more capable and cover more hardware, the catalog numbers will climb further. Microsoft has levers it could pull—more frequent checkpoints, shifting AI models to Store‑delivered optional components, better compression for MSIX bundles—but none of those have materialized yet. For now, the 5 GB monthly update is the new normal on paper, while your own PC quietly downloads a sliver of the whole.