# Learn about using JavaScript with Amazon Silk Amazon Silk uses the [V8 JavaScript engine](https://developers.google.com/v8/intro) to compile and execute JavaScript. Using the Amazon Silk **Settings** menu, users can enable or disable JavaScript. The setting is enabled by default. ![JavaScript setting toggle showing Allowed recommended status with toggle enabled.](http://docs.aws.amazon.com/silk/latest/developerguide/images/silk-shared-javascript.png) When JavaScript is disabled, Silk ignores the content of ` ``` Here's the output of the above markup rendered by Amazon Silk with JavaScript disabled: ![Test Script heading with message indicating JavaScript is disabled or not supported.](http://docs.aws.amazon.com/silk/latest/developerguide/images/javascript_disabled_page.png) ## JavaScript Loading Though not specific to Amazon Silk, the following recommendations for loading JavaScript can improve the performance of your website. + Wherever practical, combine multiple external script files into a single file to improve page load time. + Avoid including duplicate scripts on a page. + Include external CSS files before external scripts. Otherwise script loading may block style sheet loading. And include script files as far down the page as possible. HTML parsing is blocked by the downloading and execution of scripts. + Don't put inline scripts between included CSS files and other resources. Like an external script, an inline script can prevent a CSS file from downloading in parallel to other resources. In general, it's best to avoid inline scripts altogether and instead include external JavaScript files. + Use minified JavaScript. Minified JavaScript files are smaller and therefore download faster. Available tools for compressing JavaScript include [UglifyJS](https://github.com/mishoo/UglifyJS), [Closure Compiler](https://developers.google.com/closure/compiler/), and [YUI Compressor](http://yui.github.io/yuicompressor/). + Consider using the [async](http://www.w3schools.com/tags/att_script_async.asp) and [defer](http://www.w3schools.com/TAGs/att_script_defer.asp) attributes in your script elements. With `async` set, a script is downloaded asynchronously and then executed, blocking HTML parsing. With `defer` set, a script is downloaded asynchronously and then executed after HTML parsing has completed. To learn more about improving load times for scripts, see the following resources: + [Properly including stylesheets and scripts](https://developers.google.com/speed/articles/include-scripts-properly) + [14 Rules for Faster-Loading Web Sites](http://stevesouders.com/hpws/rules.php) + [Deep dive into the murky waters of script loading](http://www.html5rocks.com/en/tutorials/speed/script-loading/)