Microsoft's Copilot Studio has made headlines by harnessing .NET and WebAssembly to run C# directly in the browser. Earlier this year, the team documented their transition from .NET 6 to .NET 8, reporting significant speed gains. Now, they've taken another leap—upgrading to .NET 10. This latest move brings a suite of enhancements that streamline deployment, reduce download sizes, and boost runtime efficiency. In this article, we break down the five key improvements that Copilot Studio gained from moving to .NET 10 on WebAssembly. From simpler upgrades to smarter asset management, these changes highlight how .NET continues to evolve for modern web applications.
1. Seamless Upgrade from .NET 8 to .NET 10
Upgrading an existing .NET 8 WebAssembly application to .NET 10 is remarkably straightforward. For Copilot Studio, it involved little more than updating the target framework moniker in their .csproj files and verifying that all dependencies were compatible. The team reported no major hurdles, and the .NET 10 build is now running smoothly in production. This frictionless migration underscores .NET's commitment to backward compatibility, allowing developers to adopt new versions without costly rewrites. The transition also meant that Copilot Studio could immediately benefit from the latest performance optimizations and tooling improvements without disrupting their release schedule.
2. Automatic Fingerprinting Eliminates Manual Work
One of the most welcome changes in .NET 10 for WebAssembly apps is automatic fingerprinting of resources. When you publish a WebAssembly application, each asset's filename now includes a unique identifier. This provides built-in cache-busting and integrity guarantees—no manual intervention required. Previously, Copilot Studio had to read the blazor.boot.json manifest, run custom PowerShell scripts to rename files with SHA256 hashes, and pass integrity arguments from JavaScript. With .NET 10, all that boilerplate disappears. Resources are imported directly from dotnet.js, fingerprints are part of published filenames, and integrity validation happens automatically. The team was able to delete their custom renaming script and simplify the client-side resource loader, reducing maintenance overhead.
3. Enhanced Integrity and Cache-Busting Without Custom Scripts
Building on the fingerprinting feature, .NET 10 delivers a more robust approach to asset integrity. In earlier versions, ensuring that downloadable files hadn't been tampered with required extra JavaScript code and manual hash checking. Now, the framework handles integrity validation natively, based on the embedded fingerprints. This not only improves security but also simplifies the client-side logic. Additionally, the automatic cache-busting ensures that users always receive the latest versions of WASM files after a deployment, eliminating stale cache issues that could cause runtime errors. For Copilot Studio, this meant retiring their custom validation logic while retaining all existing caching strategies unchanged—a clear win for both developers and users.
4. Smaller Downloads with WasmStripILAfterAOT
Another headline improvement is that WasmStripILAfterAOT is now enabled by default for AOT (Ahead-of-Time) builds. In .NET 8, this setting existed but defaulted to false; you had to opt in. With .NET 10, after methods are compiled to WebAssembly, the original Intermediate Language (IL) is automatically stripped from the published output. This significantly reduces the download size of the AOT engine, because the IL code is no longer needed at runtime. For Copilot Studio, which ships a combined JIT and AOT package, this means lower bandwidth consumption and faster load times for users. The team noted that files deduplicated between the two engines remain shared, but the stripped AOT assemblies are now noticeably smaller.
5. Clever Dual-Engine Strategy for Best Performance
Copilot Studio employs an advanced packaging approach to get the best of both worlds: fast startup and high execution speed. They ship a single npm package containing both a JIT (Just-In-Time) engine for quick initial loads and an AOT engine for peak steady-state performance. At runtime, both engines are loaded in parallel. The JIT engine handles early interactions while the AOT engine compiles in the background. Once ready, control smoothly transitions to AOT. Because WasmStripILAfterAOT produces assemblies that no longer match their JIT counterparts, fewer files can be deduplicated—but the overall package remains lean thanks to .NET 10's optimizations. This dual-engine strategy ensures that users experience minimal startup delay without sacrificing long-term responsiveness.
In conclusion, Copilot Studio's upgrade to .NET 10 on WebAssembly demonstrates the tangible benefits of staying current with the .NET platform. Developers gain automatic fingerprinting, stronger integrity guarantees, smaller AOT downloads, and a smoother upgrade path—all while maintaining the flexibility to mix JIT and AOT engines for optimal performance. As .NET continues to evolve, these enhancements position WebAssembly applications for even greater efficiency and reliability in the browser.