# Options

## paths
Type: `String|Array`  
Default: Directory of input file.

Specifies directories to scan for @import directives when parsing. Default value is the directory of the source, which is probably what you want.

## compress
Type: `Boolean`  
Default: `false`

Compress output by removing some whitespaces.

## cleancss
Type: `Boolean`  
Default: `false`

Compress output using [clean-css](https://npmjs.org/package/clean-css).

## ieCompat
Type: `Boolean`  
Default: `true`

Enforce the css output is compatible with Internet Explorer 8.

For example, the [data-uri](https://github.com/cloudhead/less.js/pull/1086) function encodes a file in base64 encoding and embeds it into the generated CSS files as a data-URI. Because Internet Explorer 8 limits `data-uri`s to 32KB, the [ieCompat](https://github.com/cloudhead/less.js/pull/1190) option prevents `less` from exceeding this.

## optimization
Type: `Integer`  
Default: `null`

Set the parser's optimization level. The lower the number, the less nodes it will create in the tree. This could matter for debugging, or if you want to access the individual nodes in the tree.

## strictImports
Type: `Boolean`  
Default: `false`

Force evaluation of imports.

## strictMath
Type: `Boolean`  
Default: `false`

When enabled, math is required to be in parenthesis.

## strictUnits
Type: `Boolean`  
Default: `false`

When enabled, less will validate the units used (e.g. 4px/2px = 2, not 2px and 4em/2px throws an error).

## syncImport
Type: `Boolean`  
Default: `false`

Read @import'ed files synchronously from disk.

## dumpLineNumbers
Type: `String`  
Default: `false`

Configures -sass-debug-info support.

Accepts following values: `comments`, `mediaquery`, `all`.

## relativeUrls
Type: `Boolean`  
Default: `false`

Rewrite urls to be relative. false: do not modify urls.

## customFunctions
Type: `Object`  
Default: none

Define custom functions to be available within your LESS stylesheets. The function's name must be lowercase and 
return a primitive type (not an object or array). In the function definition, the first argument is the less
object, and subsequent arguments are from the less function call. Values passed to the function are not simple 
primitive types, rather types defined within less. See the LESS documentation for more information on the available types.

## report
Choices: `false` `'min'` `'gzip'`  
Default: `false`

Either do not report anything, report only minification result, or report minification and gzip results. This is useful to see exactly how well Less is performing, but using `'gzip'` can add 5-10x runtime task execution.

Example ouput using `'gzip'`:

```
Original: 198444 bytes.
Minified: 101615 bytes.
Gzipped:  20084 bytes.
```

## sourceMap
Type: `Boolean`  
Default: `false`

Enable source maps.

## sourceMapFilename
Type: `String`  
Default: none

Write the source map to a separate file with the given filename.

## sourceMapBasepath
Type: `String`  
Default: none

Sets the base path for the less file paths in the source map.

## sourceMapRootpath
Type: `String`  
Default: none

Adds this path onto the less file paths in the source map.