Overview overview

HTML Template Language (HTL), supported by Adobe Experience Manager (AEM), aims to provide a highly productive enterprise-level web framework that enhances security. It also enables HTML developers without Java knowledge to participate better in AEM Projects.

Introduced in AEM 6.0, the HTML Template Language is the preferred and recommended server-side template system for HTML in AEM. For web developers who need to build robust enterprise websites, the HTML Template Language helps to achieve increased security and development efficiency.

Increased Security increased-security

HTML Template Language (HTL) enhances site security by automatically applying context-aware escaping to all output variables, making it more secure than most other template systems. HTL makes this approach possible because it understands the HTML syntax, and uses that knowledge to adjust the required escaping for expressions, based on their position in the markup. This method can result in expressions placed in href or src attributes to be escaped differently from expressions placed in other attributes, or elsewhere.

While the same result can be achieved with template languages like JSP, there the developer must manually ensure that the proper escaping is applied to each variable. As a single omission or mistake in the applied escaping is potentially sufficient to cause a cross-site scripting (XSS) vulnerability, Adobe decided to automate this task with HTL. If needed, developers can still specify a different escaping on the expressions, but with HTL the default behavior is much more likely to correspond to the desired behavior, reducing the likelihood of errors.

Simplified Development simplified-development

The HTML Template Language is easy to learn and its features are purposely limited to ensure that it stays simple and straight-forward. It also has powerful mechanisms for structuring the markup and invoking logic, while always enforcing strict separation of concerns between markup and logic. HTL is standard HTML5, using expressions and data attributes to annotate the markup with dynamic behavior. This approach maintains the validity and readability of the markup. The evaluation of the expressions and data attributes is done entirely server-side and is not visible on the client-side, where any desired JavaScript framework can be used without interfering.

These capabilities let HTML developers without Java knowledge to edit HTL templates, integrate into the development team, and streamline collaboration with full-stack Java developers. And vice versa, it lets Java developers to focus on the back-end code without worrying about HTML.

Reduced Costs reduced-costs

Increased security, simplified development, and improved team collaboration, translates for AEM Projects in reduced effort, faster time to market (TTM), and lower total cost of ownership (TCO).

Re-implementing the Adobe.com site with HTML Template Language has shown that project costs and duration are reduced up to approximately 25%.

The diagram above shows the following improvements in efficiency potentially made possible by HTL:

Video Introduction video

The following video from an AEM Gems session, gives an overview of the purpose of HTL as well as implementation examples.

Please note that the video refers to HTL by its former name, Sightly.

Next Steps next-steps

Now that you know the objectives and advantages of HTL, you can get started with the language. See Getting Started with the HTML Template Language.