Where Windows never reigned - 3/6

Machine-translated page

This English version was produced by automatic AI translation. Only the French version is reviewed by the author, so it remains the authoritative reference. Spotted a mistake or an awkward turn of phrase? Please report it by opening a pull request — contributions are welcome.

Second category: the segments where Windows was never the dominant system — there was no Windows to replace. These markets were already held by Unix (often proprietary: Solaris, AIX, HP-UX, IRIX), and it is Linux and BSD that took over from Unix. On this ground, the real loser is not Windows: it is yesterday’s proprietary Unix.

Web servers#

Unix’s dominance here is overwhelming and long-standing. But before quoting a figure, one must understand how it is produced: the web “market shares” in circulation come from surveys that do not all measure the same thing, and the gap between them is considerable.

Yet they all rest on the same technique: sending an HTTP request to a site and reading the Server header of the response — the line where the server announces itself (Apache, nginx, Microsoft-IIS…). What sets them apart is not how they read, but which sites they query. Two independent biases follow:

  • The reading sees only the front-end server. If the site is behind a CDN or a reverse proxy, you read the CDN, not the origin machine. This bias only bites where CDNs are widespread — massively so in 2026, very little before 2010.
  • The chosen population does not necessarily represent the real web. Counting every domain name, or only large enterprises’ sites, or the million most-visited sites, gives very different pictures.

A word on terminology, because the Netcraft surveys — the most cited — do not count the same thing. The basic distinction: a hostname is a domain name that responds (example.com, www.example.com, blog.example.com…), whereas a site is real web content. One site can respond under several hostnames, and millions of hostnames lead to no real site at all (the parked domains, bought but empty). Hence three breakdowns:

  • hostnames: every domain that responds, parked domains included;
  • active sites: only those serving real content, parked domains excluded;
  • the busiest sites (Top Million Busiest Sites): the million sites receiving the most traffic.

The table below places the four most-cited surveys on the two biases, and gives each one’s result in OS shares (see the note that follows on this conversion):

Survey (date)Population — unit countedDoes the reading reflect the real machine? (CDN)Does the population reflect the real web? (scope)Result (OS share)
W3Techs (Jul. 2026)top 10M popular sites — the siteNo: in 2026, the big sites are behind CDNsYes, broadlyUnix ~92% (Linux ~62%, unspecified “Unix” ~30%, BSD ~0.1%) · Windows ~8%
Netcraft — hostnames (Jul. 2014)every domain that responds — the hostnameYes: hosted directly, no CDNNo: inflated by parked domainsUnix ~62% · Windows ~38%
Netcraft — busiest sites (Apr. 2009)the million most-visited sites — the sitePartly (CDNs emerging)Yes: reflects real usageUnix ~81% · Windows ~19%
Port80 — Fortune 1000 (2003)1,000 large US enterprises — the corporate siteYes (before CDNs)No: only large US commercial sites (pro-IIS vendor)Windows ~54% (IIS); rest mixed

A note on the last column: W3Techs measures the OS directly, but Netcraft and Port80 measure the web server, from which the OS is inferred. Windows’s share is derived from IIS, which runs only on Windows — so it is a floor. The rest is easy to read for Netcraft (Apache and nginx, almost always on Unix; Apache on Windows exists but is rare), but not for Port80 (2003): beyond IIS (54%, Windows), the remaining ~46% mix Apache (~18%, Unix), Netscape Enterprise Server (~21%) — multi-platform (Solaris and other Unix, but also Windows NT), whose Server header does not reveal the OS: unattributable (probably mostly Unix, iPlanet being a Sun product, but the survey does not quantify it) — and various others (~7%). Hence, for Port80, a simple Windows floor, with no Unix figure. The Linux/BSD breakdown, finally, is available only from W3Techs: of the ~92% Unix, Linux is explicitly identified for ~62%, about 30% announce themselves only as “Unix” without specifying the variant, and BSD remains marginal (~0.1%, almost all FreeBSD).

The contrast is stark. Where the population reflects real usage, Unix dominates by far — ~81% against ~19% for Windows on the million busiest sites (Netcraft, April 2009), Windows appearing there only through IIS. The only two figures that fed the opposite idea — a Windows strong on the web, which Microsoft was happy to promote — came from a biased population:

  • either inflated by parked domains (IIS’s “peak” at 37.5% of hostnames in July 2014, where Microsoft came first by that count, while the Microsoft post celebrating it admits itself that “Apache is still far ahead in active sites”);
  • or narrow: the 54% of IIS measured by Port80 in 2003, but only across Fortune 1000 sites, a terrain of large US accounts, measured by a vendor that sold IIS tools.

In 2026, IIS has all but vanished from the exposed layer of the web: 91.9% of sites whose system is identified run on Unix (Linux leading), against 8.3% for Windows, and IIS now powers only about 3% of identified servers (W3Techs, reading of 26 July 2026). One caveat, now structural: these very large sites sit behind CDNs that mask their origin system — what we observe is that IIS is no longer the visible layer, not necessarily that it has disappeared from the origin machines.

Sources:

Supercomputers#

All 500 of the world’s most powerful supercomputers run on Linux — without interruption since 2017 (June 2026 list: 500 out of 500). The number one, LineShine (National Supercomputing Centre in Shenzhen, China), a CPU-only machine that took the lead in June 2026, runs Kylin OS, a Chinese Linux distribution; the American El Capitan (Lawrence Livermore), now second and GPU-based, runs Red Hat Enterprise Linux.

Here again, this is not a defeat for Windows: this market was historically on proprietary Unix, and Windows never counted in it. The last appearance of a Windows system in the TOP500 ranking dates to June 2015 (a single system, in 436th place); since November 2015, none at all.

A word on what a supercomputer is: a machine assembling tens of thousands of processors — today often accelerated by GPUs (but not always), which then provide most of the power — that is, millions of compute cores, for massively parallel computation: materials science, aerodynamics, climate and nuclear simulation, astrophysics.

We are not talking here about AI model training clusters: they also rely on GPUs, but form a separate category, with dedicated hardware optimised for the low-precision math of AI — whereas the TOP500 ranks on the double precision (FP64) of scientific computing. They have their own section below. A supercomputer’s power is measured in FLOPS (floating-point operations per second); the best now exceed the exaFLOPS, i.e. a billion billion operations per second.

Sources:

CDNs (content delivery networks)#

A CDN brings content (videos, images, pages) closer to users through servers spread around the world. None runs on Windows — and, notably, it is not always Linux. Netflix’s Open Connect appliances, which serve an enormous share of the world’s video traffic, run on FreeBSD (BSD, not Linux). The other big players — Cloudflare, Akamai, Fastly — run on a heavily customised version of Linux.

Sources:

The public cloud#

The cloud is the heart of modern computing, and Windows is a minority there — including on Microsoft’s own platform. In May 2026, Microsoft states that more than two-thirds of its customers’ virtual-machine cores on Azure run on Linux. Since Azure is, by nature, the cloud most favourable to Windows, one can reasonably estimate that Windows accounts for less than a third of public-cloud instances overall — this is a deduction, absent a consolidated public measurement across all providers, but the order of magnitude is hardly in doubt.

This imbalance is even sustained by licensing rules. Since 1 October 2019, Microsoft has restricted the reuse of Windows Server licences on competing clouds (AWS, Google, Alibaba), while the “Azure Hybrid Benefit” — which makes such reuse almost free — remains reserved for Azure. Running Windows outside Azure therefore costs more — enough to trigger regulatory action on both sides of the Channel. The competitors’ complaints have subsided (CISPE settled with Microsoft in 2024, Google withdrew its own in late 2025), but the matter is not closed for all that: it has passed into the hands of the regulators themselves. The European Commission opened its own investigation into Microsoft’s cloud in late 2025 (under the DMA), and the UK’s CMA concluded in 2025 that competition was being harmed. So many incentives, for other clouds’ customers, to choose Linux.

Sources:

Containers and Kubernetes#

The container — the building block that transformed software deployment over the past decade — is not a product but a primitive of the Linux kernel: it rests on cgroups and namespaces, internal Linux mechanisms. Windows arrived much later and remains marginal: it eventually offered its own Windows containers (since Windows Server 2016), but to run Linux containers — the vast majority — it has to go through a Linux virtual machine (WSL2). The model, like the ecosystem, remains Linux.

Kubernetes, the orchestrator that became the standard, illustrates this: its control plane runs only on Linux; Windows is admitted only as a secondary compute node, with limited features. The Cloud Native Computing Foundation’s annual survey (published in January 2026) shows that 82% of container users run Kubernetes in production — an ecosystem entirely Linux by construction.

Sources:

Network equipment#

The routers and switches that carry the Internet do not run on Windows, but on systems of the Unix family. Juniper’s Junos rests on FreeBSD (BSD). Cisco’s systems (NX-OS, IOS-XR) and Arista’s EOS rest on Linux — Cisco’s IOS-XR having even migrated from QNX (a proprietary Unix) to Linux over successive versions. Here again, Windows never had a place in this historically Unix market.

Sources:

Mainframes#

IBM’s mainframes, which still handle a considerable share of the world’s banking transactions, run on z/OS, a proprietary IBM system descended from the mainframe lineage — never on Windows. Notably, IBM introduced Linux there (Linux on Z, the LinuxONE line), to the point that 91 of the 100 largest mainframe customers use it and more than a third of installed compute capacity runs on Linux. The mainframe, too, thus illustrates Linux’s advance on ground that was never Windows’s.

Sources:

AI training servers#

The infrastructure that trains large AI models is natively Linux. NVIDIA’s DGX systems — the reference for GPU training — ship with DGX OS, a distribution based on Ubuntu. The orchestration of training clusters (Slurm, Kubernetes) is likewise native to Linux. From the machine to the orchestrator, this infrastructure is therefore, in effect, entirely Linux.

Sources:

Film, visual effects, and animation#

The making of computer-generated imagery and visual effects is a little-known — and old — Linux stronghold. In the 1990s, VFX ran on Unix workstations (SGI on IRIX); at the turn of the 2000s, the industry moved to Linux, where it has stayed. Today, studios and render farms run on Linux — specifically the Enterprise Linux 9 (“EL9”) family: RHEL 9 and its Rocky and AlmaLinux derivatives — so much so that a joint initiative, the VFX Reference Platform (backed by the studios, the Academy Software Foundation, Autodesk, and Epic), sets EL9 as its system target.

The chain’s flagship tools all run on Linux: compositing with Nuke (Foundry), simulation with Houdini (SideFX), animation with Maya (Autodesk), rendering with Arnold or RenderMan (Pixar). Most are cross-platform (Windows, macOS, Linux); in the studios and on the render farms, they run on Linux. One goes further: Flame, Autodesk’s high-end finishing software, runs only on Linux and macOS.

One caveat, though: editing (assembling the shots) partly escapes Linux — Avid Media Composer and Adobe Premiere Pro workstations run on Windows or macOS; only DaVinci Resolve (Blackmagic) is also offered on Linux. But on the technical core of the image — 3D, simulation, compositing, rendering — the industry chose Linux, not Windows.

Sources:

Chip design (EDA)#

Designing integrated circuits relies on highly specialised software — EDA (Electronic Design Automation) — dominated by three vendors: Cadence, Synopsys, and Siemens EDA. It is another Linux stronghold: the reference tools for chip design (Cadence Virtuoso, Synopsys Design Compiler, Siemens Calibre) run on Linux (RHEL and its Rocky/AlmaLinux derivatives), on server farms. Like VFX, the sector came from Unix (Sun/Solaris and HP-UX workstations) and moved to Linux in the 2000s.

Don’t generalise to all electronics, though: PCB design — another branch of EDA — remains largely on Windows; its reference tool, Altium Designer, is Windows-only. It is chip design (semiconductors), the most compute-heavy part, that is a Linux stronghold.

Sources:

Certified avionics#

In certified flight controls (the DO-178C standard), the requirement for certification and traceability — proving, line by line, that the software behaves as specified — demands systems built for safety from the outset: real-time operating systems (RTOS) — that is, able to guarantee a response within a bounded, predictable time — and proprietary ones. The main ones are VxWorks (Wind River), INTEGRITY-178 (Green Hills), and PikeOS (SYSGO). None is Windows, none is Linux in the ordinary sense. Windows is not among them — not even Windows CE: that system was real-time, yet it was never designed for the certification of critical avionics.

Sources:

Suggest an edit

By Yanal-Yves FARGIALLA • Updated on August 18, 2026 (AI-assisted writing, final review by the author)
Unless otherwise noted, this content is licensed under CC BY-SA 4.0. CC BY-SA 4.0