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


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Status: Archived

status: inactive

This repository has been archived and is no longer maintained.

JavaScript code prettifier

Announcement: Action required is going away.

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:
<script src=""></script>


Put code snippets in <pre class="prettyprint">...</pre> or <code class="prettyprint">...</code> and it will automatically be pretty-printed.

<pre class="prettyprint">class Voila {
  // Voila
  static const string VOILA = "Voila";

  // will not interfere with embedded <a href="#voila2">tags</a>.


For which languages does it work?

The comments in prettify.js 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 src/lang-lisp.js and submit a pull request.

How do I specify the language of my code?

You don't need to specify the language since PR.prettyPrint() will guess. You can specify a language by specifying the language extension along with the prettyprint class:

<pre class="prettyprint lang-html">
  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 <code> element inside the <pre> and using language-java style classes:

<pre class="prettyprint"><code class="language-java">...</code></pre>

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 linenums class to turn on line numbering. If your code doesn't start at line number 1, you can add a colon and a line number to the end of that class as in linenums:52. For example:

<pre class="prettyprint linenums:4"
>// This is line 4.

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

You can use the nocode class to identify a span of markup that is not code:

<pre class="prettyprint">
int x = foo();  /* This is a comment  <span class="nocode">This is not code</span>
  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 prettyPrint 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 PR.prettyPrint which will confuse it.

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

Prettify adds <span> with classes 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 <pre class="prettyprint ..."> you can use a comment or processing instructions that survives processing instructions: <?prettify ...?> works 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, prettify.css.

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

li.L0, li.L1, li.L2, li.L3,
li.L5, li.L6, li.L7, li.L8 {
  list-style-type: decimal !important;


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


Apache License 2.0