{"slug": "coreclr", "name": "CoreCLR", "category": "dev-libs", "category_name": "Libraries and frameworks", "description": "", "recommenders": 4, "commenters": 6, "warners": 0, "score": 3.834, "rising": -1.31, "first": "2025-11-06", "latest": "2026-07-28", "why": "we're excited to see how much better performance will be on CoreCLR.", "why_is_quote": true, "has_verdict": false, "sentiment": {"recommend": 4, "neutral": 1, "compare": 1, "warn": 0}, "spark": [1, 2, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0], "listed": true, "loved": [], "caveat": "", "short_quote": "we're excited to see how much better performance will be on CoreCLR.", "kind": "", "icon": false, "domain": null, "github_repo": null, "official_url": "https://github.com/dotnet/runtime", "pricing": "", "aliases": ["CoreCLR"], "verdict": null, "praise": [{"label": "", "summary": "", "quotes": [{"id": 785428432, "item_id": 49089277, "url": "https://news.ycombinator.com/item?id=49089277", "by": "Rohansi", "date": "2026-07-28", "stance": "recommend", "quote": "we're excited to see how much better performance will be on CoreCLR.", "excerpt": "I have my doubts! I work on Rust (the video game) and we're excited to see how much better performance will be on CoreCLR. However, we were confused by the switch from \"Mono replaced with CoreCLR with these breaking changes Unity 6.8\" [1] to \"Mono replaced with CoreCLR with no breaking changes in Unity 7 [2], with Unity 6.8 off the roadmap [3]\". [1] https://discussions.unity.com/t/path-to-coreclr-2026-upgrade-guide/1", "context": "works on the game Rust", "use_case": "", "switched_from": "", "story": "Watching Go's new garbage collector move through the heap"}, {"id": 742874675, "item_id": 46429667, "url": "https://news.ycombinator.com/item?id=46429667", "by": "iliketrains", "date": "2025-12-29", "stance": "recommend", "quote": "I am hoping that Unity will deliver on the CoreCLR dream.", "excerpt": "Sure, we could use Burst to speed up some strategic parts, but that would not help with the core of the game. To give some context, things are very complex in our game, we have fully dynamic terrain with terrain physics (land-slides), advanced path-finding of hundreds of vehicles (each entity has its own width and height clearance), trains, conveyors and pipes carrying tens or even hundreds of thousands of individual", "context": "", "use_case": "", "switched_from": "", "story": "Unity's Mono problem: Why your C# code runs slower than it should"}, {"id": 742699379, "item_id": 46418711, "url": "https://news.ycombinator.com/item?id=46418711", "by": "torginus", "date": "2025-12-29", "stance": "recommend", "quote": "using CoreCLR for most code", "excerpt": "I think you've unfortunately got suckered in by Unity marketing wholesale, and things would stand to be cleared up a bit. Unity's whole shtick is that they make something horrible, then improve upon it marginally. The ground reality is that these performance enhancement schemes still fall very much short of just doing the basic sensible thing - using CoreCLR for most code, and writing C++ for the truly perf critical ", "context": "", "use_case": "", "switched_from": "", "story": "Unity's Mono problem: Why your C# code runs slower than it should"}, {"id": 733374913, "item_id": 45835932, "url": "https://news.ycombinator.com/item?id=45835932", "by": "neonsunset", "date": "2025-11-06", "stance": "recommend", "quote": "it's nowhere near as capable as CoreCLR", "excerpt": "If anything, the Mono runtime is what prevents heavier (ab)use of SIMD types in the standard library, or at least it causes additional required effort to make it not regress in performance since it's nowhere near as capable as CoreCLR. You can find the overview of relevant high-level types here: https://learn.microsoft.com/en-us/dotnet/standard/simd For low-level types and historical context: https://devblogs.microso", "context": "", "use_case": "", "switched_from": "", "story": "The state of SIMD in Rust in 2025"}]}], "caveats": [], "who": [{"by": "Rohansi", "context": "works on the game Rust", "url": "https://news.ycombinator.com/item?id=49089277", "date": "2026-07-28"}], "tags": [], "use_cases": [], "compared": [{"slug": "mono", "name": "Mono", "co": 5, "switched_from": 0, "switched_to": 0}, {"slug": "unity", "name": "Unity", "co": 4, "switched_from": 0, "switched_to": 0}], "makers": [], "threads": [{"url": "https://news.ycombinator.com/item?id=46414819", "title": "Unity's Mono problem: Why your C# code runs slower than it should", "mentions": 3}, {"url": "https://news.ycombinator.com/item?id=49045474", "title": "Watching Go's new garbage collector move through the heap", "mentions": 2}, {"url": "https://news.ycombinator.com/item?id=45826348", "title": "The state of SIMD in Rust in 2025", "mentions": 1}], "sentiment_by_month": {"2025-11": {"recommend": 1}, "2025-12": {"compare": 1, "recommend": 2}, "2026-01": {}, "2026-02": {}, "2026-03": {}, "2026-04": {}, "2026-05": {}, "2026-06": {}, "2026-07": {"neutral": 1, "recommend": 1}, "2026-08": {}, "2026-09": {}, "2026-10": {}}, "quotes": [{"id": 785428432, "item_id": 49089277, "url": "https://news.ycombinator.com/item?id=49089277", "by": "Rohansi", "date": "2026-07-28", "stance": "recommend", "quote": "we're excited to see how much better performance will be on CoreCLR.", "excerpt": "I have my doubts! I work on Rust (the video game) and we're excited to see how much better performance will be on CoreCLR. However, we were confused by the switch from \"Mono replaced with CoreCLR with these breaking changes Unity 6.8\" [1] to \"Mono replaced with CoreCLR with no breaking changes in Unity 7 [2], with Unity 6.8 off the roadmap [3]\". [1] https://discussions.unity.com/t/path-to-coreclr-2026-upgrade-guide/1", "context": "works on the game Rust", "use_case": "", "switched_from": "", "story": "Watching Go's new garbage collector move through the heap"}, {"id": 785339282, "item_id": 49083705, "url": "https://news.ycombinator.com/item?id=49083705", "by": "pjmlp", "date": "2026-07-28", "stance": "neutral", "quote": "with CoreCLR already in preview for mobile platforms", "excerpt": "A Jurassic GC introduced in Mono, that due to Unity not wanting to pay Xamarin for updates, meant it was mostly frozen in the days of Unity/Xamarin early collaboration. Unity preferred to go down the route of HPC#, Burst compiler and IL2CPP, and is still maybe one to two years to fully migrate to modern .NET. Meanwhile in Redmond, Mono is almost gone, with CoreCLR already in preview for mobile platforms, https://devb", "context": "", "use_case": "", "switched_from": "", "story": "Watching Go's new garbage collector move through the heap"}, {"id": 742874675, "item_id": 46429667, "url": "https://news.ycombinator.com/item?id=46429667", "by": "iliketrains", "date": "2025-12-29", "stance": "recommend", "quote": "I am hoping that Unity will deliver on the CoreCLR dream.", "excerpt": "Sure, we could use Burst to speed up some strategic parts, but that would not help with the core of the game. To give some context, things are very complex in our game, we have fully dynamic terrain with terrain physics (land-slides), advanced path-finding of hundreds of vehicles (each entity has its own width and height clearance), trains, conveyors and pipes carrying tens or even hundreds of thousands of individual", "context": "", "use_case": "", "switched_from": "", "story": "Unity's Mono problem: Why your C# code runs slower than it should"}, {"id": 742699379, "item_id": 46418711, "url": "https://news.ycombinator.com/item?id=46418711", "by": "torginus", "date": "2025-12-29", "stance": "recommend", "quote": "using CoreCLR for most code", "excerpt": "I think you've unfortunately got suckered in by Unity marketing wholesale, and things would stand to be cleared up a bit. Unity's whole shtick is that they make something horrible, then improve upon it marginally. The ground reality is that these performance enhancement schemes still fall very much short of just doing the basic sensible thing - using CoreCLR for most code, and writing C++ for the truly perf critical ", "context": "", "use_case": "", "switched_from": "", "story": "Unity's Mono problem: Why your C# code runs slower than it should"}, {"id": 742646097, "item_id": 46415381, "url": "https://news.ycombinator.com/item?id=46415381", "by": "Rochus", "date": "2025-12-28", "stance": "compare", "quote": "I made measurements with Mono and CoreCLR some years ago", "excerpt": "That's interesting. I made measurements with Mono and CoreCLR some years ago, but only with a single thread, and I came to the conclusion that their performance was essentially the same (see https://rochus.hashnode.dev/is-the-mono-clr-really-slower-than-the-coreclr). Can someone explain what benchmarks were actually used? Was it just the \"Simple benchmark code\" in listing 1?", "context": "", "use_case": "", "switched_from": "", "story": "Unity's Mono problem: Why your C# code runs slower than it should"}, {"id": 733374913, "item_id": 45835932, "url": "https://news.ycombinator.com/item?id=45835932", "by": "neonsunset", "date": "2025-11-06", "stance": "recommend", "quote": "it's nowhere near as capable as CoreCLR", "excerpt": "If anything, the Mono runtime is what prevents heavier (ab)use of SIMD types in the standard library, or at least it causes additional required effort to make it not regress in performance since it's nowhere near as capable as CoreCLR. You can find the overview of relevant high-level types here: https://learn.microsoft.com/en-us/dotnet/standard/simd For low-level types and historical context: https://devblogs.microso", "context": "", "use_case": "", "switched_from": "", "story": "The state of SIMD in Rust in 2025"}]}