The long-called-for migration of digital ads from using Adobe Flash to HTML5 is becoming a reality. It's a shift underscored by, among other developments, Amazon's switch to HTML5-only promos earlier this month, as well as The Washington Post last week committing to publishing its content on Facebook via the markup language.

With that in mind, the Interactive Advertising Bureau today is updating its guidelines for brand marketers and ads-focused technologists on how to best employ HTML5 software. The main items addressed in the second version of the handbook, dubbed the IAB HTML5 for Digital Advertising Guide, include techie advice on creative assets optimization for desktop and mobile viewers, recommendations on video and animation executions, specifics about how to utilize shared content libraries and suggestions on text and fonts.

The handbook's 1.0 version was last updated in July 2013.

"It is the continuation of the migration from the Flash world to an HTML5 world," Scott Cunningham, svp at IAB and general manager of the IAB Tech Lab, told Adweek. "It gives us an opportunity for cross-screen digital security layers and better optimized—from a technical perspective—delivery mechanisms. It is a fresh update to the guidelines that were established a couple of years ago."

As Cunningham alluded to, one of the chief reasons publishers are adopting HTML5 lies in security; they're responding to Web portals like Yahoo and MSN getting attacked by from malvertising, which injects malicious promos into legitimate digital ad networks. Another key advantage HTML5 has over Flash is that HTML5 more easily renders multimedia content as it is capable of running on any computer and mobile device—whether iPhone, Android, iPad, Microsoft Surface, etc. Some gadgets cannot render Flash-powered content.

It's been a pretty big turn of events for HTML5 developers in the last year, as there were observers declaring the system dead toward the end of 2014. That's clearly no longer the case.

Meanwhile, the IAB's guide has also been reorganized to break down elements that specifically relate to ad designers, developers and ad servers. These features include a list of potential tools for HTML5 ad development as well as detailed information on compatibility with different Web browsers.

The report—put together by the IAB Technology Laboratory—coincides with the kick off of the annual IAB MIXX Conference today.