Or, focusing mainly on language and runtime characteristics,
where do you think Crystal works well, and where does Rust work well?
Rust is a great choice when you need low overhead, since it doesn’t have a garbage collector and is designed with safety in mind. It works well for high-availability and high-performance systems (like those used by AWS or Cloudflare), as well as heavy desktop applications, browsers, or rewriting legacy code (such as old C++ codebases).
Crystal is more suitable for higher-level systems or applications that don’t require Rust’s strict safety guarantees. Both can be used in similar contexts, since their performance can be comparable, but they involve different trade-offs (for example, Rust syntax and Crystal garbage collector).
For the work I do – security tooling, protocol implementation, API integrations – Crystal hits a sweet spot that Rust doesn’t.
I came from Ruby. A decade of it with just a few scripts and utilizing tools written by security researchers. Crystal reads like Ruby with a compiler and a type system, which means the translation cost from “idea” to “working implementation” stays low. When I’m implementing a protocol from an RFC spec I want to think about the protocol, not fight the borrow checker while I’m still figuring out whether my field offset assumptions are even correct. Crystal lets me do that.
The static binary story matters a lot in my domain. crystal build --static targeting musl gives me a zero-dependency binary I can drop into any Linux environment without installing anything. For security tooling that’s not a nice-to-have, it’s an operational requirement. Constrained environments, air-gapped networks, targets where you don’t control what’s installed. Crystal solves that cleanly.
Rust wins when memory safety is a hard architectural requirement – kernel work, browser engines, anywhere a use-after-free becomes a CVE rather than just a bug to fix. The borrow checker’s guarantees are worth the cost in those domains.
For application-level systems programming though? Crystal gives you performance, nil safety, compile-time type checking, and drop-and-run deployment without Rust’s learning curve or syntax overhead. For someone building security tools and protocol libraries coming from a Ruby background, it’s not a close comparison.
IMO Crystal strikes a nice balance between safety and conciseness. Rust can be safer, but the language imposes so much more on the programmer to provide that safety. You often end up having to appease the compiler because, even though your code may be safe due to the semantics under which it executes, the compiler can’t guarantee it’s safe so it will refuse to compile it. I like that better than how Go handles safety[1] but I much prefer how Crystal does it.
Here is a nice direct comparison I wrote several years ago:
I was comparing performance in the post, but I also put the benchmark code into the post so folks could see the difference in how the code feels to them. The Rust code was as concise as I could get it to be and it’s not even the safe way to write it because panics in Rust are not equivalent to Crystal exceptions.
Meanwhile, the Crystal version is even more concise, structured in a way that’s easier to understand[2] and it’s just as safe.
Rust is much more popular, do not have GC, have better safety guaranties and well, is better designed so things like incremental compilation or assignment to struct fields weren’t existential problems for it. I wonder about generic inheritance, but huh, it doesn’t have inheritance so perhaps it’s not a problem for it too.
But when you need to do something as simple as “pass two elements of array to function by (mutable) reference”, madness starts from “discover split_at_mut in stdlib that could help” and goes straight to “if you need three elements, it is easier to download crate that was made specially for this problem”. So I’ll stick to Crystal, lol.
My reasons (on why Crystal) are similar as the ones from @jgaskins.
I use Crystal in low-level scenarios and infrastructure, areas in which Go and Rust are normally recommended.
Not only Crystal presents a similar level of performance (sometimes it wins), but it does it with an unmatched balance of productivity+simplicity and performance+efficiency.
Crystal is not perfect (as any other language) but it is already the official language in our small company/startup. And we are so satisfied, that we are not looking back.