Companies Using WebAssembly

WebAssembly is the hardest row in our Programming Languages table to read, because developers rarely write it by hand. C#, Go, C++ and a growing list of other languages compile to it so they can run in a browser. As of our October 2026 crawl we count 813 domains, and 306 of them match a company record, a 37.64% match rate. Getting there took real cleaning: the raw detection list held 392 more domains, most of them casino lobbies.

What the signal catches

A domain counts when a page exposes the wasmBinary or wasmBinaryFile variables that an Emscripten-style loader creates, or loads Go's wasm_exec.js runtime. (The rule also has a response-header clause, but it reads only the page's own headers, and an HTML page doesn't send application/wasm.) So the count sees two toolchain families and misses builds that load a .wasm file without either marker; Rust builds made with wasm-bindgen rarely show up. Treat it as a floor. Our technology detection methods post explains how these rules are matched.

I fetched all 1,205 domains that passed our title filter on 16 October and opened the ones without a visible marker in a browser. 339 were gambling lobbies, 299 of them loading their scripts from one white-label casino platform's hosts, sp-slots1.com and zuvio.mx, and 53 were dead. Those 392 are out of every number on this page. Here is what the remaining 813 are:

• 347 Blazor WebAssembly apps (42.68%), 334 of them loading blazor.webassembly.js
• 143 other Emscripten or WebAssembly apps: games, PDF and image tools, barcode scanners, medical image viewers
• 71 Go apps plus 55 Remnawave proxy panels, which are Go too
• 45 FlipHTML5 flipbooks, 7 Kotlin builds and 6 Microsoft Remote Desktop web clients
• 139 that didn't answer (38), blocked our fetcher (17) or showed no WebAssembly that day (84)

Sales signal: the list is now mostly business software. Split it by toolchain before you prospect, because each group has a different buyer.

Growth trajectory

The chart has a single point, 813 domains in October 2026, because October is the first month counted after the cleaning. The uncleaned months before it wouldn't have told you much anyway. The set of domains we crawl turns over every month, with dead sites dropping out and newly found ones added, and our detection signals widen over time, so earlier movement was mostly our reach. Since 16 March 2026, 359 domains have dropped WebAssembly on at least one hostname, and only 9 of those still ran it on another hostname in mid-October.

"Strip out the casino lobbies and WebAssembly on the open web is mostly a .NET story: companies putting a C# business portal in the browser with Blazor." - Mehmet Suleyman, CEO & Co-founder at TechnologyChecker.io

Sales signal: size the market at 813 domains. It's small, and it's concentrated in one toolchain.

Who the customers are

49.48% of matched companies with a known size have 1 to 10 employees, 24.74% have 11 to 50 and 13.75% have 51 to 200. Only 12 have more than 1,000 staff. The age data is the surprise: 10.61% were founded before 1960. Those are old manufacturers and distributors with a modern .NET portal: Weldco-Beales (founded 1945) on its account portal, Herring Gas (1946) on its customer account site, Lewis Marine Supply (1956) on its ordering site. The bigger names follow the same pattern: Jackson Lewis's Checkit portal, doValue's broker portal, Avidyne's dealer portal. Blazor's own profile helps explain why these show up: of 114 large Blazor sites it checked, 20 ran standalone WebAssembly, the build our rule sees most.

Outside the business portals, the sites we verified in a browser are the kind that turn up on lists of WebAssembly demos: an in-browser database shell, a 3D globe, a design app and a webmail client all load .wasm files.

Sales signal: the buyer is the IT team or the .NET agency that built the portal. They need component libraries, hosting, authentication and testing for a C# front end.

Industry and geography

Software Development (10.92%), IT Services and IT Consulting (7.39%) and Technology, Information and Internet (6.34%) make up 24.65% of matched companies. Financial Services is 3.87%, and Wholesale ties Computer Games at 2.46%. The United States leads with 62 of the 306 matched companies, then the United Kingdom (13) and France (10). Denmark, with 9, punches above its size: housing associations run a tenant portal called MinSide on a minside. subdomain, built with Blazor.

Sales signal: Danish and wider Nordic public-sector and housing portals are a small but tidy pocket. The same portal repeats across associations.

Switching: what the data can and can't say

There's no switching table for WebAssembly, and there shouldn't be. It doesn't replace PHP or Java; it sits beside them. 71 domains run PHP and WebAssembly today, out of 85 that ever had both, which is a PHP site with a compiled tool on one page. The Remnawave panels make the same point from another angle: 55 separate operators, 19 of them on .ru domains, running the same open-source proxy panel, published on GitHub under AGPL-3.0, whose web UI loads Go's runtime.

"A WebAssembly hit tells you the toolchain, not the vendor. Blazor, Go and Emscripten builds each point to a different buyer." - Mehmet Suleyman, CEO & Co-founder at TechnologyChecker.io

Sales signal: split this list by toolchain before outreach. A Blazor portal, a Go app and an Emscripten game have nothing in common except the file format.

The stack around it

Percentages are of the 813 clean live domains. Blazor runs on 45.63%, with Microsoft ASP.NET on 22.88% and IIS on 22.51%: one Microsoft stack. Cloudflare is in front of 28.17%, and WordPress shows on 13.28%. Nuxt.js is down to 1.72%; before the cleaning it was the casino fleet's framework, since all 13 lobbies we checked were Nuxt apps. WebAssembly 3.0 was completed in September 2025 with garbage collection, which the standard's own announcement says languages such as Java, Kotlin and Dart now use; our crawl shows only 7 Kotlin builds so far.

Sales signal: for a .NET component or hosting vendor, the IIS and ASP.NET overlap is the qualifier. For a game or graphics tool vendor, the Emscripten group is the list.

Key takeaways

• 813 domains after removing 339 gambling lobbies and 53 dead domains from the 1,205 we fetched.
• Blazor WebAssembly is the largest group, 347 domains, mostly business portals.
• Go accounts for 126, including 55 self-hosted Remnawave panels.
• The count is a floor: builds without an Emscripten-style variable or Go's runtime aren't seen.
• Older manufacturers and distributors are a real segment, with 10.61% founded before 1960.

Sales applications

Outreach template: "Your [portal name] at [detection URL] runs on Blazor WebAssembly. Teams with a C# front end in the browser often run into [load time / testing / component gaps]. Can I show you how others handle it?"

Targeting: filter WebAssembly domains that also run Blazor or ASP.NET and keep those with a company match.

Competitive angle: JavaScript framework consultancies can pitch rebuilds to the older standalone Blazor apps; .NET vendors can pitch upgrades to the newer Blazor Web App model.

The full list of WebAssembly domains, with company size, industry and the URL where we saw each build, is on TechnologyChecker.io: 813 domains and 306 matched companies from our October 2026 crawl.