HTML5 is a universal language for building beautiful, engaging content that can run across desktop, smartphones, and tablets, unlike flash. HTML5 is especially useful for rich media creatives because rendering is done by the browser, so you don't have to rely on third-party plug-ins (such as Flash). HTML5 is a standard for structuring and delivering web content and is constructed as a combination of HTML, JavaScript and CSS assets.
The market is already moving to this standard: as consumers continue to use mobile devices more frequently, publishers are migrating to HTML5 video players and browsers are introducing power saving plugins that prevent Flash ads from working properly.
Google Web Designer is a powerful and intuitive HTML5 authoring tool, which is completely free to download and use. Download it here | GWD components and templates here
For DoubleClick Studio users, you can use HTML5 layouts within the tool to turn your assets into HTML5 ad units in a few minutes. Find out more
Similar to Studio Layouts, Adwords provides a Ready Ad Gallery of templates that can be used to turn assets into HTML5 ads in minutes for AdWords campaigns. Find out more