The application offers a Quick Look Extension for macOS 10.15 Catalina and later for previewing source files. Inside it uses Highlight to render source code with syntax highlighting.

Syntax Highlight is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY.

If you like this application and find it useful, buy me a coffee!

• Installation
  • Download precompiled release
  • Install with Homebrew
  • Note for the precompiled release
  • Build from source
• Enable the Quick Look extension
• File format management
  • Supported formats
• Application settings
  • Rendering settings
    • External Language Server support
    • Version control support
  • Plain files
  • Colors
  • Inquiry file
• Command line interface
• Add support to a custom format
• FAQ
• Known bugs
• Note for developers
  • Info about decoding dynamic UTI identifiers
  • Other useful links
• Credits

You can install the application in various ways. When the main application is launched it automatically checks for updates.

After installation, the application must be launched at least once to allow the system to detect the Quick Look extension. See below for instructions on how to enable the Quick Look extension.

Head over to the releases page to view the latest version. Move Syntax Highlight.app into the Applications folder.

Syntax Highlight can also be installed via Homebrew. If you have not installed Homebrew, follow the simple instructions here. After that, install the current version of Syntax Highlight with the following command:

The precompiled app is codesigned and notarized.

The release application is compiled as a universal binary (Intel and Apple silicon processor).

After cloning remember to fetch submodules:

To use the Quick Look preview you must launch the Application at least once. In this way the Quick Look Extension will be discovered by the system and will be available in the System preferences > Extensions > Quick Look.

The Quick Look Extension uses the Uniform Type Identifier (UTI) to handle the supported formats (and not simply the file name extension). Inside the definition on an UTI there are the list of extensions and mime type associated with it.

Some file types are directly associated to a UTI by the system. Other formats are registered by the owner application. In this way some extensions can be associated to multiple UTIs based on the applications currently installed. For this reason, this application supports many UTIs even if they are apparently redundant.

MacOS 10.15 Catalina does not allow to manage some file formats including (but not limited to): .xml, .plist, .html, .ts, .dart, .txt, common images (.jpg, .gif, .png), …

On macOS 11 Big Sur, the system allows you to manage these previously unauthorized extensions: .plist.

On macOS 12 Monterey, the system allows you to manage these previously unauthorized extensions: .xml.

Most programming languages are supported. The application can also handle some plain files without extension.

• Ada (.ada)
• Adobe Acrobat Sequence files (.sequ) as XML
• Adobe Flash ActionScript source files (.as)
• Adobe Flex files (.mxml) files as XML
• Adobe JSX script files (.jsx)
• Adobe UPX Javascript (.psjs)
• Apple loctable (.loctable) as plist (XML)
• Apple workflow (.wflow) as plist (XML)
• AppleScript (.scpt, .applescript, .ascr) automatically decompiled with osadecompile
• Apple shell script files (.command)
• Assembler source files (.asm, .s79)
• Astro files (.astro) as JSX.
• Autolit files (.au3, .a3x)
• Azkaban flow files (.flow) as YAML
• ATL files (.atl)
• (G)AWK files (.awk)
• Bash Script files (.bash)
• Bezel (.bezel) as plain text
• BibTex (.bib)
• C shell script files (.csh)
• C source files (.c, .h)
• C# source files (.cs)
• C++ source files (.cpp, .cp, .c++, .cc, .cxx, .hpp, .hh, .hxx, .ipp )
• ClojureScript (.cli, .cljs, .cljc, .edn)
• CMake files (.cmake)
• CocoaPod files (.podspec) as Ruby
• CoffeeScript source files (.coffee)
• ColdFusion files (.cfc, .cfm, .cfml)
• Configuration files (.conf)
• Configuration profiles (.mobileconfig) as XML
• Crystal language (.cr)
• CSON source files (.cson)
• CSS files (.css)
• Cuda files (.cu) as C++
• D (.d)
• Dart source files (.dart) .dart is reserved by macOS and cannot be handled.
• Designspace files (.designspace) as XML
• Diff files (.diff, .patch)
• Dockerfile (.dockerfile)
• Document Type Definition (.dtd)
• DOS batch files (.bat, .cmd)
• Dylang (.dylan)
• ECore files (.ecore)
• Eiffel project files (.ecf) as XML
• Eiffel source files (.e, .ex, .exs)
• Elixir files (.ex, .exs, .heex)
• ePub Navigation Center eXtended (.ncx) as XML.
• ePub Open Packaging Format (.opf) files as XML.
• Erlang source files (.erl, .hri)
• F# source files (.fsx, .fs)
• fish source files (.fish)
• FonTool files (.ttx) as XML.
• Fortran source files (.f, .for, .f90, .f95)
• GCC linked files (.ld, .map, .d)
• Gdscript (Godot engine) (.gd).
• Gleam (.gleam)
• Golang source files (.go)
• Google Earth KML Document files (.kml) as XML
• Gradle source files (.gradle)
• Graphics Language Transmission Format (.gltf) as JSON
• Groovy source files (.groovy)
• Haskell source files (.hs, .lhs)
• HTML Abstraction Markup Language (.haml)
• IDL source files (.pro)
• INF files (.inf)
• INI configuration files (.ini, .cfg)
• Inno source files (.iss)
• INO source files (.ino)
• IntelliJ IDEA module (.iml)
• Interface Builder Storyboard (.storybard) as XML
• Interface Builder XIB (.xib) as XML
• Java Compiled Class (.class) require javap to decompile
• Java Properties files (.properties) as INI
• Java Server Page files (.jsp)
• Java source code (.java, .jav)
• Java Web Start (.jnlp)
• JavaFX ML (.fxml)
• JavaScript files (.js, .jscript, .javascript, .mjs, .jsm)
• JSON files (.json, .jsonc, .json5) ** On macOS 13 Ventura with Apple Silicon the .json extension is reserved by the system and cannot be handled.**
• JSON Canvas (.canvas) as JSON
• JSON Line files (.jsonl) as JSON
• Julia source files (.jl)
• Jupyter Notebook files (.ipynb) as JSON
• Kermeta source files (.kmt)
• Korn Shell script files (.ksh)
• Kotlin source files (.kt, .kts)
• LESS stylesheet (.less)
• Lilypond files (.ly, .ily)
• Lisp source files (.lisp, .lsp, .asd, .el)
• Logos source files (.xm)
• Lua source files (.lua)
• Makefile files (.mk, .mak)
• MAMEdev layout files (.lay) as XML.
• Markdown files (.md, .rmd): please use QLMarkdown which allows you to choose whether to display formatted output or the highlighted source code.
• Media Presentation Description (.mpd) as XML.
• MetaTrader (.mq4, .mq5) files as CPP.
• MF source files (.mf)
• Microsoft Active Server Page files (.asp, .aspx)
• Microsoft PowerShell files (.psm1, .psd1, .ps1)
• Microsoft Visual Studio C# Project (.csproj) as XML
• MiniScript files (.ms)
• NextFlow (.nf) as Groovy (Java)
• Nim source files (.nim)
• Nix Expression Language (.nix)
• Node CommonJS module (.cjs)
• Objective-C source files (.m)
• Objective-C++ source files (.mm)
• OCaml source files (.ml, .mll, .mly)
• OpenSSH RSA public key (.pub) as plain text
• OpenTimelineIO files (.otio) as JSON
• OpenType feature file specification (.fea)
• OPML (Outline Processor Markup Language) files (.opml) as XML
• Oracle PL/SQL files (.fnc, .prc, .trg, .pks, .pkb, .pck, .tps, .tpb, .typ, .tab, .avt, .con, .sqs, .vw, .mvw, .trg) as SQL
• Paradox files (.sc)
• Pascal source files (.pas)
• Patch files (.patch, .diff)
• PDE source files (.pde, .ino)
• Perl script files (.pl, .pm, .t)
• Planning Domain Description Language (.pddl) as Lisp
• PHP source files (.php, .php3, .php4, .ph3, .ph4, .phtml)
• Project Object Model files (.pom) as XML
• Properties files (.properties) as INI
• Property List files (.plist) dynamically decompiled with plutil On macOS 10.15 Catalina .plist is reserved by the system and cannot be handled.
• Python source files (.py, .py3, .pyi)
• R (.r)
• Racket (.rkt) as Lisp
• RAML (.raml) as YAML
• Rexx (.rex, .rexx)
• RDF files (.rdf)
• README files (.readme) as plain text
• reStructuredText document (.rst)
• Rez files (.r)
• Ruby on Rails files (.rhtml, .erb, .rjs)
• Ruby Gems file (.gemfile)
• Ruby script (.rb, .rbw)
• Rust source files (.rs)
• SageMath files (.sage) as Python
• SAS files (.sas)
• SASS/SCSS files (.scss)
• Scala source files (.sc, .sbt, .scala)
• Scala scale file format (.scl) as plain text
• Scheme source files (.scm, .ss, .sls, .sps, .sld, .sch) as Lisp
• Shell script files (.bashrc, .zshrc, .sh)
• Smali (.smali) as plain text.
• Solidity source files (.sol)
• SQL files (.sql)
• Standard ML source files (.ml)
• Stata files (.do, .ado) as plain text
• Steam app manifest files (.acf) as plain text.
• Svelte (.svelte) as HTML
• Swift source files (.swift)
• Symfony Twig files (.twig)
• TCL source files (.tcl)
• Tenex C Shell script files (.tcsh)
• Terraform files (.tfvars, .tfstate, .tf, .hcl) as YAML
• TeX and LaTeX files (.tex, .sty, .cls, .latex, .ltx, .texi, .ctx, .sty)
• Text files (.txt, .text)
• TOML files (.toml)
• TypeScript files (.ts, .tsx, .cts, .mts) .ts and .mts are reserved by macOS and cannot be handled.
• Unity document (.unity) as YAML
• Visual Studio Code Workspace (.code-workspace) as JSON
• Verilog HDL files (.v, .vl)
• VHDL source files (.vhd, .vhdl)
• VIM script files (.vim)
• Visual Basic source files (.vb, .bas, .basic, .vbs)
• Vue source files (.vue)
• XAML source files (.xaml) as XML
• Xcode entitlement files (.entitlements) (dynamically decompiled with plutil) as XML
• Xcode localizable strings files (.strings, .stringsdict) (dynamically decompiled with plutil) as XML _ Xcode scheme as XML
• XHTML files (.xhtml)
• XML files (.xml) Before macOS 12 Monterey .xml is reserved by the system and cannot be handled.
• XSD Schema files (.xsd, .xquery, .xq, .xu)
• XUL files (.xul)
• YAML files (.yaml)
• Z shell script files (.zsh)
• Zig source files (.zig)
• Zig Object Notation files (.zon) as JSON.

With the standalone application you can customize the rendering settings.

You can show advanced settings using the relative command on the view menu.

You can set the settings for all supported formats on the General tab.

You can also override the global options for some formats on the Formats tab.

When customizing the settings for a specific format, these options will be available:

Advanced users can customize the single format to use an external Language Server:

When using an external Language Server the preprocessor and the data limit settings are ignored.

Some format have a preconfigured custom settings to handle the data (for example java compiled class file can be decompiled before render).

You can also enable the support of common VCS to highlight the added/edited/removed lines from last commit.

In the General settings you must enable the VCS support. Then you can customize the path of git and mercurial binary. The you can choose the colors used to mark the changed lines. On every format you can also customize the colors.

On RTF mode, the VCS plugin can be disabled if the syntax language defines more keyword groups than those defined in the theme.

The Application can preview plain files without an extension whose format is unknown.

Only files recognized by the system with one of the following UTIs can be handled:

• public.data
• public.item
• public.content
• public.unix-executable

Files with an extension or associated to a dynamic UTI will not be handled. Files that have a only one dot as the first character in their name (like .gitignore, .env, ...) are considered to have no extension.

Unknown files are analyzed with the system utility /usr/bin/file for recognize mime type and encoding. No preprocessor is applied before analyzing the file.

Files recognized as images are handled by displaying the content within a web page (even if the rendering engine set in the settings is RTF). To be displayed correctly, the image format must be supported by WebKit.

On macOS 12 Monterey images and even, audio, movies and PDF files are displayed with the native Quick Look interface.

For other binary files it is possible to display a hex dump.

For text files, syntax highlighting is tried.

You can specify a criteria for the file name and the mime type to apply a syntax highlighting and/or a specific display format. The criteria are evaluated in the order in which they are set.

If no display format is set, the system will try to derive it starting from the mime type.

Note that some files with no extension can be recognized by macOS with a UTI if they have the com.apple.FinderInfo extended attributed set.

The Application has a GUI to customize the color schemes.

Standard schemas provided by highlight cannot be edited but can be duplicated and then customized.

For every tokens of a color scheme you can also set a custom inline CSS style. Some basic CSS style can be handled also by the RTF engine, but for a best view you must choose the HTML render engine. For this reason the preview of the Color Scheme always uses the HTML engine.

Please note that the inline CSS style is not put inside the HTML style attribute but embedded on the global <style> tag inside the class style definition of the token. So you can define a custom CSS style sheet that override the inline settings.

When inserting the style of a theme token it is possible to indicate whether this should override the default values for color and font style. If you want to use the custom theme with the RTF rendering engine it is required not to override the standard values.

Color schemes that uses inline CSS style are highlighted by an icon.

With the advanced settings enabled you can also customize the appearance of the Language Server Protocol tokens.

With the Inquiry window you can see if a specific file type is handled by the Quick Look Extension and also if it is supported by highlight.

Alternatively you can see the UTI of a file with this Terminal command:

It's likely that I didn't associate all the possible extensions managed by highlight. If you found an unhandled format please send me the output of above command.

Only the formats supported by highlight can be managed by this application.

A syntax_highlight_cli command line interface (CLI) is available to perform batch conversion.

The tool is located inside the Syntax Highlight.app/Contents/Resources folder (and should not be moved outside).

From the Application menu you can create a symbolic link into /usr/local/bin folder.

The CLI interface uses the same settings as the Quick Look extension, but you can override it if you wish.

The highlighted data is printed to the stdout or writed to file if you use the -o option.

** You cannot manually add support for a new file format.** This operation must be done during compilation time. Any attempt to manipulate the application causes the code signature to be violated, making it unusable!

See also the FAQ.

The problem may be due to several causes:

1. The application is not registered under system extensions.
2. Another application is handling the preview instead of Syntax Highlight.
3. Some application has registered the format with unrecognized UTI.
4. You are trying to view unsupported formats.
5. You are trying to view a format reserved by the system.

If the problem affects all file formats it must related to points 1. and 2., so try one or more of these action:

• Try the RTF render engine, especially for macOS versions earlier than 12 Monterey.
• Drag the application on the trash and back to the Applications folder and then relaunch.
• Check in the System Preferences > Extensions > Quick Look if the Syntax Highlight extension is present and checked.
• In the System Preferences > Extensions > Quick Look, drag the Syntax Highlight extension on the top.
• In the System Preferences > Extensions > Quick Look disable other extensions one at a time until you find the one that conflicts.

If the problem affects only a specific format it is possible that this was registered by some application with a non-standard UTI. Check the UTI with the Inquiry window and send me the value. The support for each format must be defined at compile time.

Also remember that some common files cannot be handled by third party extension because are reserved by the system (for example, .ts, .html, …).

No, Apple does not allow this functionality.

This is a deliberate choice. Most users want to see the formatted output and not the source code of their markdown files. If you need to view the markdown files (also with the possibility of choosing whether to show the formatting or the source code) I have developed QLMarkdown.

It depends… first the format must be handled by highlight. Check in the Inquiry window if the file is supported. If is supported please send me the UTI associated to the file. You can also view the UTI with this terminal command:

mdls -name kMDItemContentType -name kMDItemContentTypeTree filename.ext

Some common files cannot be handled by third party extension because are reserved by the system (for example, .ts, .html, …).

You can customize the behavior for files with no extension yourself. See Plain files settings.

This Application only generate the Quick Look Preview and does not provide a thumbnail service for the Finder icon.

When the Debug option is enabled (on the advanced settings) on your Desktop folder will be created two files for the last preview action:

• colorize.log with the log of the highlight process.
• colorize.hml|rtf the output of the last rendering process.

• On Big Sur you cannot scroll the preview inside a Quick Look window dragging the scrollbars with the mouse. This is a Big Sur bug. You can scroll only with a mouse/trackpad gesture. Fixed on maxOS 12 Monterey.
• On macOS earlier than 12 Monterey, soft word wrap with RTF engine reacts when the window is enlarged but not when it is reduced.
• Icons of the custom file format are disabled on Catalina (cause an application freeze).
• In RTF mode the colors may be slightly lighter than what is set (probably due to the different handling of color profile).
• Typescript .ts format cannot be handled because is reserved by macOS and associated to the mpeg video stream format.
• If a Quick Look window is opened when the system switch the theme appearance, the contents will not be refreshed to the new style.

Starting from macOS 10.15.0 Catalina the qlgenerator APIs are deprecated.

This project consists of these components:

• A Standalone Application to set the preferences.
• A Quick Look Extension to preview the source files.
• An XPC service that generate the preview and pass the formatted data to the application or the Quick Look Preview.

MacOS 10.15 Catalina require sandboxed extension that prevent the execution of external processes (like shell script). To work around this problem, it is possible to use an XPC service that may have different security policies than the application / extension that invokes it. In this case the XPC service is not sandboxed.

The XPC service is executed automatically when requested by the application or the Quick Look Extension. After closing the Quick Look preview the process is automatically closed after some seconds releasing the resources.

The Application and the Quick Look Extension can preview files showing the formatted code as HTML, inside a WKWebView, or as RTF inside a NSTextView. Especially in Big Sur, the use of WebKit within the Quick Look Preview has numerous bugs, so before macOS 12 Monterey, the suggested rendering engine is RTF. From macOS 12 Monterey, the plugin adopt the new data based Quick Look API.

The settings are stored in ~/Library/Preferences/org.sbarex.SourceCodeSyntaxHighlight.plist. Custom themes and styles are saved in ~/Library/Application Support/Syntax Highlight.

The application embed the Highlight engine that is build inside the Xcode project.

• https://gist.github.com/jtbandes/19646e7457208ae9b1ad
• https://alastairs-place.net/blog/2012/06/06/utis-are-better-than-you-think-and-heres-why/
• whomwah/qlstephen#87
• https://www.cocoanetics.com/2012/09/fun-with-uti/
• whomwah/qlstephen#87 (comment) :

Ok, so according to the source I references above, I would do the following:

• https://stackoverflow.com/questions/16943819/where-do-uti-come-from/18014903#18014903

List all registered UTIs:

• handle extension from command line (https://stackoverflow.com/questions/66546696/how-to-enable-and-debug-a-macos-file-provider-extension , https://stackoverflow.com/questions/34898903/what-do-the-prefixes-in-the-output-of-macos-pluginkit-mean/36839118#36839118 , https://kevin.deldycke.com/2019/07/macos-commands/ ):

List all registered Quick Look plugins:

İnfo about a plugin:

https://eclecticlight.co/2024/11/04/how-does-quicklook-create-thumbnails-and-previews-with-an-update-to-mints/

https://eclecticlight.co/2024/11/02/a-brief-history-of-icons-thumbnails-and-quicklook/

https://eclecticlight.co/2024/10/31/how-sequoia-has-changed-quicklook-and-its-thumbnails/

https://mjtsai.com/blog/2024/11/05/sequoia-no-longer-supports-quicklook-generator-plug-ins/

https://eclecticlight.co/2025/10/25/explainer-how-does-macos-recognise-file-types/

Developed by sbarex with ❤️.

Highlight is developed by Andre Simon.

Dos2unix is developed by Erwin Waterlander.

This application was inspired by anthonygelibert/QLColorCode and NSGod/qlstephen.

If you find this application useful, buy me a coffee.