A micro web server framework on top of the official Swift HTTP API


Swift 4 macOS tuxOS Travis

NOTE: The repository containing the asynchronous variant of MicroExpress now lives at Noze.io. Images have been updated. This repository will eventually revert to the synchronous HTTP API variant.

A micro server framework on top of the Swift Server WG HTTP API.

Swift NIO: The Swift NIO version moved over MicroExpress/NIO. This is probably what you are looking for :-)

It adds an Express like API on top of the low level Swift Server WG HTTP API.

import MicroExpress

let app = Express()

app.get("/moo") { req, res, next in
  try res.send("Muhhh")
app.get("/json") { _, res, _ in
  try res.json([ "a": 42, "b": 1337 ])
app.get("/") { _, res, _ in
  try res.send("Homepage")


This package is part of the Always Right Institute's blog series about the Swift Server Workgroup's offical Swift HTTP API.

Please checkout Part 3 of our blog series to learn what this is about. This is a tiny framework, for a more full featured, synchronous Express-like API in Swift, have a look at ExExpress (as used in ApacheExpress). Noze.io comes w/ an asynchronous variant (but is using Dispatch, not Swift NIO - stay tuned).

Using the Package

Micro Hello World in 5 minutes (or in 30s using the swift-xcode image below):

$ mkdir MicroHelloWorld && cd MicroHelloWorld
$ swift package init --type executable

Update Package.swift to include the dependency:

// swift-tools-version:4.0
import PackageDescription

let package = Package(
  name: "MicroHelloWorld",
  dependencies: [
    .package(url: "https://github.com/AlwaysRightInstitute/MicroExpress.git", 
  targets: [
    .target(name: "MicroHelloWorld",
            dependencies: [ "MicroExpress" ])

Change the main.swift from print("Hello World") into:

import MicroExpress

let app = Express()

app.get("/") { req, res, next in
  res.send("Hello World")

$ swift build
$ swift run

Done. Access via: http://localhost:1337/

Building the Package


Choose the easy way using the swift-xcode Swift NIO image, or take the hard way and use swift package generate-xcodeproj.


brew install swiftxcode/swiftxcode/swift-xcode-nio
swift xcode link-templates # <-- important!
  1. Create new project (Command-Shift-N or File/New/Project ...)
  2. choose macOS / Server / Swift NIO template
  3. check desired options
  4. build and run, and then have fun!

swift package generate-xcodeproj

Important: This creates a few schemes in the Xcode project. Make sure to select the right one when building & running.

$ swift package generate-xcodeproj
Fetching ...
Cloning ...
Resolving ...
generated: ./MicroExpress.xcodeproj

$ open MicroExpress.xcodeproj

macOS /Linux Command Line

$ swift build
Fetching ...
Cloning ...
Resolving ...
Compile ...
Compile Swift Module ...
Compile Swift Module 'MicroExpress' (9 sources)
Linking ./.build/x86_64-apple-macosx10.10/debug/MicroExpress

Linux via macOS Docker

$ docker run --rm \
  -v "${PWD}:/src" \
  -v "${PWD}/.docker.build:/src/.build" \
  swift:4.0.3 \
  bash -c 'cd /src && swift build'
Unable to find image 'swift:4.0.3' locally
4.0.3: Pulling from library/swift
8f7c85c2269a: Pull complete 
9783e1c76d2b: Pull complete 
Digest: sha256:6978675b95f749b54eab57163c663d45b25c431c6d50cb5b2983062a55cea3c6
Status: Downloaded newer image for swift:4.0.3
Compile ...
Compile Swift Module ...
Compile Swift Module 'MicroExpress' (9 sources)
Linking ./.build/x86_64-unknown-linux/debug/MicroExpress
Fetching ...
Cloning ...
Resolving ...

$ file .docker.build/x86_64-unknown-linux/debug/MicroExpress
  ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked ...



MicroExpress is brought to you by the Always Right Institute and ZeeZide. We like feedback, GitHub stars, cool contract work, presumably any form of praise you can think of.

Want a Video Tutorial?


  • Swift Tools 4.0.0
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Last updated: Tue Mar 14 2023 08:10:58 GMT-0500 (GMT-05:00)