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5.6K Stars 948 Forks Apache License 2.0 473 Commits 229 Opened issues


An embeddable script that makes source-code snippets in HTML prettier.

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JavaScript code prettifier

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An embeddable script that makes source-code snippets in HTML prettier.

  • Works on HTML pages.
  • Works even if code contains embedded links, line numbers, etc.
  • Simple API: include some JS & CSS and add an onload handler.
  • Lightweights: small download and does not block page from loading while running.
  • Customizable styles via CSS. See the themes gallery.
  • Supports all C-like, Bash-like, and XML-like languages. No need to specify the language.
  • Extensible language handlers for other languages. You can specify the language.
  • Widely used with good cross-browser support. Powers and

See an example.


  • Include the script tag below in your document:
  • See Getting Started to configure that URL with options you need.
  • Look at the skin gallery and pick styles that suit you.


Put code snippets in

and it will automatically be pretty-printed.
class Voila {
  // Voila
  static const string VOILA = "Voila";

// will not interfere with embedded tags. }


For which languages does it work?

The comments in

are authoritative but the lexer should work on a number of languages including C and friends, Java, Python, Bash, SQL, HTML, XML, CSS, JavaScript, Makefile, and Rust.

It works passably on Ruby, PHP, VB, and Awk and a decent subset of Perl and Ruby, but because of commenting conventions, doesn't work on Smalltalk, OCaml, etc. without a language extension.

Other languages are supported via extensions:

Apollo; Basic; Clojure; CSS; Dart; Erlang; Go; Haskell; Lasso; Lisp, Scheme; LLVM; Logtalk; Lua; MATLAB; MLs: F#, Ocaml,SML; Mumps; Nemerle; Pascal; Protocol buffers; R, S; RD; Rust; Scala; SQL; Swift; TCL; LaTeX; Visual Basic; VHDL; Wiki; XQ; YAML

If you'd like to add an extension for your favorite language, please look at

and submit a pull request.

How do I specify the language of my code?

You don't need to specify the language since

will guess. You can specify a language by specifying the language extension along with the
  The lang-* class specifies the language file extensions.
  File extensions supported by default include:
    "bsh", "c", "cc", "cpp", "cs", "csh", "cyc", "cv", "htm", "html", "java",
    "js", "m", "mxml", "perl", "pl", "pm", "py", "rb", "sh", "xhtml", "xml",

You may also use the HTML 5 convention of embedding a

element inside the
 and using 
style classes:

It doesn't work on "obfuscated code sample"?

Yes. Prettifying obfuscated code is like putting lipstick on a pig — i.e. outside the scope of this tool.

Which browsers does it work with?

It's been tested with IE 6, Firefox 1.5 & 2, and Safari 2.0.4. Look at the tests to see if it works in your browser.

What's changed?

See the changelog.

Why doesn't Prettyprinting of strings work on WordPress?

Apparently wordpress does "smart quoting" which changes close quotes. This causes end quotes to not match up with open quotes.

This breaks prettifying as well as copying and pasting of code samples. See WordPress's help center for info on how to stop smart quoting of code snippets.

How do I put line numbers in my code?

You can use the

class to turn on line numbering. If your code doesn't start at line number
, you can add a colon and a line number to the end of that class as in
. For example:
// This is line 4.

How do I prevent a portion of markup from being marked as code?

You can use the

class to identify a span of markup that is not code:
int x = foo();  /* This is a comment  This is not code
  Continuation of comment */
int y = bar();

For a more complete example see the issue #22 testcase.

I get an error message "a is not a function" or "opt_whenDone is not a function"

If you are calling

via an event handler, wrap it in a function. Instead of doing:
addEventListener('load', PR.prettyPrint, false);

wrap it in a closure like:

addEventListener('load', function(event) { PR.prettyPrint(); }, false);

so that the browser does not pass an event object to

which will confuse it.

How can I customize the colors and styles of my code?

Prettify adds

es describing the kind of code. You can create CSS styles to matches these classes.

See the theme gallery for examples.

I can't add classes to my code (because it comes from Markdown, etc.)

Instead of

 you can use a comment or processing
instructions that survives processing instructions: 
as explained in Getting Started.

How can I put line numbers on every line instead of just every fifth line?

Prettify puts lines into an HTML list element so that line numbers aren't caught by copy/paste, and the line numbering is controlled by CSS in the default stylesheet,


The following should turn line numbering back on for the other lines:


Please use the official support group for discussions, suggestions, and general feedback.


Apache License 2.0

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