/ Highlighting

A lightweight and flexible Swift syntax highlighter for blogs

A lightweight and flexible Swift syntax highlighter for blogs


A fast, lightweight and flexible Swift syntax highlighter for blogs, tools and fun!

Welcome to Splash - a fast, lightweight and flexible Swift syntax highlighter. It can be used to generate code sample HTML for a blog post, to turn a string of Swift code into a fully syntax highlighted image, or to build custom developer tools.


Splash can be used either as a library in your own Swift Package Manager-powered tool or script, or by using one of the three built-in command line tools that act as frontends for the Splash library.

🌍 On the web

Thanks to my good friend Gui Rambo, you can try out Splash directly in your browser! His web tool lets you use Splash to generate either HTML or an image, by simply pasting Swift code into a text box.

👉 splash.rambo.codes

🖥 On the command line

The easiest way to get started building things with Splash is to use one of the three built-in command line tools that each enable you to use Splash in different ways.


SplashHTMLGen uses Splash's HTML output format to generate an HTML string from Swift code. You simply pass it the code you want to highlight as an argument and HTML is returned as standard output.

For example, if you call it like this:

$ SplashHTMLGen "func hello(world: String) -> Int"

You'll get the following output back:

<span class="keyword">func</span> hello(world: <span class="type">String</span>) -> <span class="type">Int</span>

To be as flexible as possible, Splash doesn't hardcode any colors or other CSS attributes in the HTML it generates. Instead it simply assigns a CSS class to each token. For an example of a CSS file that can be used to style Splash-generated HTML, see Examples/sundellsColors.css.

For more information about HTML generation with Splash and how to customize it, see HTMLOutputFormat.


SplashImageGen uses Splash to generate an NSAttributedString from Swift code, then draws that attributed string into a graphics context to turn it into an image, which is then written to disk.

For example, if you call it like this:

$ SplashImageGen "func hello(world: String) -> Int" "MyImage.png"

The following image will be generated (and written to disk as MyImage.png):


SplashImageGen is currently only available on macOS.


The final built-in command line tool, SplashTokenizer, is mostly useful as a debugging tool when working on Splash - but can also be interesting to use in order to see how Splash breaks down code into tokens. Given a string of Swift code, it simply outputs all of its components (excluding whitespaces).

So if you call it like this:

$ SplashTokenizer "func hello(world: String) -> Int"

You'll get the following standard output back:

Keyword token: func
Plain text: hello(world:
Type token: String
Plain text: )
Plain text: ->
Type token: Int

📦 As a package

To include Splash in your own script or Swift package, add it as a dependency and use the SyntaxHighlighter class combined with your output format of choice to highlight a string of code:

import Splash

let highlighter = SyntaxHighlighter(format: HTMLOutputFormat())
let html = highlighter.highlight("func hello() -> String")

Splash ships with two built-in output formats - HTML and NSAttributedString, but you can also easily add your own by implementing the OutputFormat protocol.


Splash is distributed as a Swift package, making it easy to install for use in scripts, developer tools, server-side applications, or to use its built-in command line tools.

Splash supports both macOS and Linux.

Before you begin, make sure that you have a Swift 4.1-compatible toolchain installed (for example Xcode 9.4 if you're on a Mac).

📦 As a package

To install Splash for use in a Swift Package Manager-powered tool or server-side application, add Splash as a dependency to your Package.swift file. For more information, please see the Swift Package Manager documentation.

🏃‍♂️ As a Marathon dependency

If you want to use Splash in a Marathon script, either add it to your Marathonfile (see the Marathon repo for instructions on how to do that), or point Marathon to Splash using the inline dependency syntax:

import Splash // https://github.com/johnsundell/splash.git

Command line tools

If you want to use Splash through one of its built-in command line tools, start by cloning the repo to your local machine:

$ git clone https://github.com/johnsundell/splash.git
$ cd Splash

To run a tool without installing it, you can use the Swift Package Manager's run command, like this:

$ swift run SplashHTMLGen "func hello(world: String) -> Int"

To install all three command line tools globally on your system, use Make:

$ make install

That will install the following three tools in your /usr/local/bin folder:


If you only wish to install one of these, compile it and then move it to /usr/local/bin, like this:

$ swift build -c release -Xswiftc -static-stdlib
$ install .build/Release/SplashHTMLGen /usr/local/bin/SplashHTMLGen