Introduction

zapline is a web framework for Rust that brings three things together:

• FastAPI-level ergonomics. You write plain async fns with typed arguments, and you get request parsing, validation, errors, and interactive OpenAPI docs automatically.
• Enterprise-grade structure. It includes dependency injection, layered configuration, lifecycle hooks, plugins, guards and policies, observability, and health checks. These are the building blocks large teams expect from Spring Boot, NestJS or ASP.NET Core.
• Top-tier performance. Thread-per-core runtimes, zero-allocation routing, and no per-request cost for features you don't use. On equal hardware, zapline outperforms axum and actix-web in its own benchmark suite.

use zapline::prelude::*;

#[get("/hello/{name}")]
async fn hello(Path(name): Path<String>) -> String {
    format!("Hello, {name}!")
}

fn main() -> std::io::Result<()> {
    App::new().mount(hello).run("0.0.0.0:8080")
}

Philosophy

1. The common case is one line. Each feature has a default that works out of the box: App::openapi(...), .plugin(Health::new()), .wrap(Cors::permissive()).
2. Everything is overridable. Defaults are built from public traits and builders, so you can swap any piece.
3. Pay only for what you use. Optional features sit behind Cargo features and extension points. An app that doesn't use metrics runs exactly the same code path as if metrics didn't exist.
4. Testable by default. app.test() runs the whole pipeline in-process with no sockets.

How this guide is organized

• Getting started gets an app running and explains the CLI.
• Core concepts covers the request pipeline: routing, extractors, responses, errors and middleware.
• Building APIs, Security, Realtime & content and Operations cover the batteries.
• The Reference lists every Cargo feature and explains how the framework is put together.