zigzap/zap: blazingly fast backends in zig


Zap is intended to become the zig replacement for the
kind of REST APIs I used to write in python with
Flask and
mongodb, etc. It can be considered to be a
microframework for web applications.

What I need for that is a blazingly fast, robust HTTP server that I can use with
zig. While facil.io supports TLS, I don’t care about HTTPS support. In
production, I use nginx as a reverse proxy anyway.

Zap wraps and patches facil.io – the C web application


Under the hood, everything is super robust and fast. My zig wrappers are fresh,
juicy, and alpha.

Here’s what works:

  • Super easy build process: zap’s build.zig now uses the up-and-coming zig
    package manager for its C-dependencies, no git submodules anymore.

    • tested on Linux and macOS (arm, M1)
  • hello: welcomes you with some static HTML
  • routes: a super easy example dispatching on
    the HTTP path
  • serve: the traditional static web server with
    optional dynamic request handling
  • sendfile: simple example of how to send
    a file, honoring compression headers, etc.
  • hello_json: serves you json
    dependent on HTTP path
  • endpoint: a simple JSON REST API example featuring a
    /users endpoint for PUTting/DELETE-ing/GET-ting/POST-ing and listing users,
    together with a static HTML and JavaScript frontend to play with.
  • mustache: a simple example using
    mustache templating.
  • endpoint authentication: a
    simple authenticated endpoint. Read more about authentication
  • http parameters: a simple example
    sending itself query parameters of all supported types.
  • cookies: a simple example sending itself a
    cookie and responding with a session cookie.
  • websockets: a simple websockets chat for the
  • Username/Password Session
    : A convenience
    authenticator that redirects un-authenticated requests to a login page and
    sends cookies containing session tokens based on username/password pairs
    received via POST request.
  • MIDDLEWARE support: chain together
    request handlers in middleware style. Provide custom context structs, totally
    type-safe, using ZIG-CEPTION. If you come from GO
    this might appeal to you.
  • MIDDLEWARE with endpoint
    Same as the example above, but this time we use an endpoint at the end of the
    chain, by wrapping it via zap.Middleware.EndpointHandler. Mixing endpoints
    in your middleware chain allows for usage of Zap’s authenticated endpoints and
    your custom endpoints. Since Endpoints use a simpler API, you have to use
    r.setUserContext() and r.getUserContext() with the request if you want to
    access the middleware context from a wrapped endpoint. Since this mechanism
    uses an *anyopaque pointer underneath (to not break the Endpoint API), it is
    less type-safe than zap.Middleware‘s use of contexts.
  • Per Request Contexts : With the introduction of
    setUserContext() and getUserContext(), you can, of course use those two in
    projects that don’t use zap.SimpleEndpoint or zap.Middleware, too, if you
    really, really, absolutely don’t find another way to solve your context
    problem. We recommend using a zap.SimpleEndpoint inside of a struct that
    can provide all the context you need instead. You get access to your
    struct in the callbacks via the @fieldParentPtr() trick that is used
    extensively in Zap’s examples, like the endpoint
  • Error Trace Responses: You can now
    call r.sendError(err, status_code) when you catch an error and a stack trace
    will be returned to the client / browser.

I’ll continue wrapping more of facil.io’s functionality and adding stuff to zap
to a point where I can use it as the JSON REST API backend for real research
projects, serving thousands of concurrent clients.

blazingly fast

Claiming to be blazingly fast is the new black. At least, zap doesn’t slow you
down and if your server performs poorly, it’s probably not exactly zap’s fault.
Zap relies on the facil.io framework and so it can’t really
claim any performance fame for itself. In this initial implementation of zap,
I didn’t care about optimizations at all.

But, how fast is it? Being blazingly fast is relative. When compared with a
simple GO HTTP server, a simple zig zap HTTP server performed really good on my

  • zig zap was nearly 30% faster than GO
  • zig zap had over 50% more throughput than GO

Elephant in the room: I was intrigued comparing to a basic rust HTTP server.
Unfortunately, knowing nothing at all about rust, I couldn’t find one and hence
tried to go for the one in The Rust Programming
Wanting it to be of a somewhat fair comparison, I opted for the multi-threaded
example. It didn’t work out-of-the-box, but I got it to work and changed it to
not read files but outputting a static text just like in the other examples.
Maybe someone with rust experience can have a look at my
wrk/rust/hello code and tell me why it’s surprisingly slow, as
I expected it to be faster than the basic GO example. I’ll enable the
GitHub discussions for this matter. My suspicion is bad performance of the

Update: Thanks to @felipetrz, I got to test against more realistic Python
and Rust examples. Both python sanic and rust axum were easy enough to

So, being somewhere in the ballpark of basic GO performance, zig zap seems to be
… of reasonable performance 😎.

See more details in blazingly-fast.md.

Getting started

$ git clone https://github.com/zigzap/zap.git
$ cd zap
$ zig build run-hello
$ # open http://localhost:3000 in your browser

… and open http://localhost:3000 in your browser.

Using zap in your own projects

If you don’t have an existing zig project, create one like this:

$ mkdir zaptest && cd zaptest
$ zig init-exe
$ git init      ## (optional)

Note 1: Zap is developed with zig master. This version of zig has the
package management features in place that are used in the following
instructions. Nix users are lucky; you can use the existing flake.nix and run
nix develop to get a development shell providing zig, and also all
dependencies to build the and run the GO, python, and rust examples for the
wrk performance tests. For mere building, nix develop .#build will only
fetch zig master.

With an existing zig project, adding zap to it is easy:

  1. Add zap to your build.zig.zon
  2. Add zap to your build.zig

To add zap to build.zig.zon:

    .name = "My example project",
    .version = "0.0.1",

    .dependencies = .{
        // zap v0.1.6-pre
        .zap = .{
            .url = "https://github.com/zigzap/zap/archive/refs/tags/v0.1.6-pre.tar.gz",
            .hash = "1220a3eab193523b30721dae56a763468b7348b3d1f0b3364d68f6d548c753a72c5a",

Then, in your build.zig‘s build function, add the following before

    const zap = b.dependency("zap", .{
        .target = target,
        .optimize = optimize,
    exe.addModule("zap", zap.module("zap"));

From then on, you can use the zap package in your project. Check out the
examples to see how to use zap.

Updating your project to the latest version of zap

You can change the URL to zap in your build.zig.zon

  • easiest: use a tagged release
  • or to one of the tagged versions, e.g. 0.0.9
  • or to the latest commit of zap

Using a tagged release

Go to the release page. Every release
will state its version number and also provide instructions for changing
build.zig.zon and build.zig.

Using a tagged version

Go to to the tags page to view all
available tagged versions of zap. From there, right click on the tar.gz link
to copy the URL to put into your build.zig.zon.

After changing the .url field, you will get an error like this at the next
attempt to zig build:

.../build.zig.zon:8:21: error: hash mismatch:
expected: 12205fd0b60720fb2a40d82118ee75c15cb5589bb9faf901c8a39a93551dd6253049,
found: 1220f4ea8be4a85716ae1362d34c077dca10f10d1baf9196fc890e658c56f78b7424
.hash = "12205fd0b60720fb2a40d82118ee75c15cb5589bb9faf901c8a39a93551dd6253049",

Note: If you don’t get this error, clean your global zig cache: rm -fr ~/.cache/zig. This shouldn’t happen with current zig master anymore.

With the new URL, the old hash in the build.zig.zon is no longer valid. You
need to take the hash value displayed after found: in the error message as
the .hash value in build.zig.zon.

Using an arbitrary (last) commit

Use the same workflow as above for tags, excpept for the URL, use this schema:

.url = "https://github.com/zigzap/zap/archive/[COMMIT-HASH].tar.gz",

Replace [COMMIT-HASH] with the full commit hash as provided, e.g. by git log.

Contribute to zap – blazingly fast

At the current time, I can only add to zap what I need for my personal and
professional projects. While this happens blazingly fast, some if not all
nice-to-have additions will have to wait. You are very welcome to help make the
world a blazingly fast place by providing patches or pull requests, add
documentation or examples, or interesting issues and bug reports – you’ll know
what to do when you receive your calling 👼.

Check out CONTRIBUTING.md for more details.

See also introducing.md for more on the state and progress of
this project.

We now have our own ZAP discord server!!!

You can also reach me on the zig showtime discord
under the handle renerocksai

Support zap

Being blazingly fast requires a constant feed of caffeine. I usually manage to
provide that to myself for myself. However, to support keeping the juices
flowing and putting a smile on my face and that warm and cozy feeling into my
heart, you can always buy me a coffee
. All donations are welcomed 🙏 blazingly fast! That being said, just saying
“hi” also works wonders with the smiles, warmth, and coziness 😊.


You build and run the examples via:

$ zig build [EXAMPLE]
$ ./zig-out/bin/[EXAMPLE]

… where [EXAMPLE] is one of hello, routes, or serve.

Example: building and running the hello example:

$ zig build hello
$ ./zig-out/bin/hello

To just run an example, like routes, without generating an executable, run:

$ zig build run-[EXAMPLE]

Example: building and running the routes example:


const std = @import("std");
const zap = @import("zap");

fn on_request(r: zap.SimpleRequest) void {
    if (r.path) |the_path| {
        std.debug.print("PATH: {s}\n", .{the_path});

    if (r.query) |the_query| {
        std.debug.print("QUERY: {s}\n", .{the_query});
    r.sendBody("<html><body><h1>Hello from ZAP!!!</h1></body></html>") catch return;

pub fn main() !void {
    var listener = zap.SimpleHttpListener.init(.{
        .port = 3000,
        .on_request = on_request,
        .log = true,
    try listener.listen();

    std.debug.print("Listening on\n", .{});

    // start worker threads
        .threads = 2,
        .workers = 2,

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