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YUI Compressor
YUI Compressor - The Yahoo! JavaScript and CSS Compressor
Usage: java -jar yuicompressor-x.y.z.jar [options] [input file]
Global Options
-h, --help Displays this information
--type <js|css> Specifies the type of the input file
--charset <charset> Read the input file using <charset>
--line-break <column> Insert a line break after the specified column number
-v, --verbose Display informational messages and warnings
-o <file> Place the output into <file>. Defaults to stdout.
JavaScript Options
--nomunge Minify only, do not obfuscate
--preserve-semi Preserve all semicolons
--disable-optimizations Disable all micro optimizations
The YUI Compressor is a JavaScript compressor which, in addition to removing
comments and white-spaces, obfuscates local variables using the smallest
possible variable name. This obfuscation is safe, even when using constructs
such as 'eval' or 'with' (although the compression is not optimal is those
cases) Compared to jsmin, the average savings is around 20%.
The YUI Compressor is also able to safely compress CSS files. The decision
on which compressor is being used is made on the file extension (js or css)
-h, --help
Prints help on how to use the YUI Compressor
Some source control tools don't like files containing lines longer than,
say 8000 characters. The linebreak option is used in that case to split
long lines after a specific column. It can also be used to make the code
more readable, easier to debug (especially with the MS Script Debugger)
Specify 0 to get a line break after each semi-colon in JavaScript, and
after each rule in CSS.
--type js|css
The type of compressor (JavaScript or CSS) is chosen based on the
extension of the input file name (.js or .css) This option is required
if no input file has been specified. Otherwise, this option is only
required if the input file extension is neither 'js' nor 'css'.
--charset character-set
If a supported character set is specified, the YUI Compressor will use it
to read the input file. Otherwise, it will assume that the platform's
default character set is being used. The output file is encoded using
the same character set.
-o outfile
Place output in file outfile. If not specified, the YUI Compressor will
default to the standard output, which you can redirect to a file.
-v, --verbose
Display informational messages and warnings.
Minify only. Do not obfuscate local symbols.
Preserve unnecessary semicolons (such as right before a '}') This option
is useful when compressed code has to be run through JSLint (which is the
case of YUI for example)
Disable all the built-in micro optimizations.
+ If no input file is specified, it defaults to stdin.
+ The YUI Compressor requires Java version >= 1.4.
+ It is possible to prevent a local variable, nested function or function
argument from being obfuscated by using "hints". A hint is a string that
is located at the very beginning of a function body like so:
function fn (arg1, arg2, arg3) {
"arg2:nomunge, localVar:nomunge, nestedFn:nomunge";
var localVar;
function nestedFn () {
The hint itself disappears from the compressed file.
+ C-style comments starting with /*! are preserved. This is useful with
comments containing copyright/license information. For example:
* Open source under the BSD License.
* Copyright 2001 Robert Penner All rights reserved.
* Open source under the BSD License.
* Copyright 2001 Robert Penner All rights reserved.
The YUI Compressor was written and is maintained by:
Julien Lecomte <>
The CSS portion is a port of Isaac Schlueter's cssmin utility.
Copyright (c) 2007-2009, Yahoo! Inc. All rights reserved.
All code specific to YUI Compressor is issued under a BSD license.
YUI Compressor extends and implements code from Mozilla's Rhino project.
Rhino is issued under the Mozilla Public License (MPL), and MPL applies
to the Rhino source and binaries that are distributed with YUI Compressor.
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