AEM 101-11: Mastering Sightly in Adobe Experience Manager – An Introductory Guide

Adobe Experience Manager (AEM)
Adobe Experience Manager (AEM)

I. Introduction

Welcome back to our AEM 101 series, where we delve into the intricacies of Adobe Experience Manager (AEM), a robust content management solution for building websites, mobile apps, and forms. Our journey so far has navigated through the fundamentals of AEM, exploring its architecture, the use of JCR (Java Content Repository), and the creation of components and templates. If you’re new here or need a refresher, I encourage you to explore the previous entries in this series.

In this installment, we turn our focus to a critical and powerful aspect of AEM: Sightly, now known officially as HTML Template Language (HTL). Sightly/HTL plays a pivotal role in AEM development, offering a secure and efficient way to develop AEM components. It’s designed to be an intuitive, HTML-like language that seamlessly integrates with AEM’s capabilities, empowering developers to build dynamic and responsive digital experiences.

As we proceed, we’ll embark on a journey to understand Sightly/HTL in depth. We’ll start with what Sightly is and why it’s essential in the AEM ecosystem. Following that, we’ll guide you through setting up your environment for Sightly development, delve into the core concepts, and eventually lead you through creating your first Sightly template. Furthermore, we’ll discuss integrating Sightly with AEM components, share best practices, and touch upon advanced features and techniques that will elevate your AEM projects to the next level.

Whether you’re a seasoned AEM developer or just starting, this guide aims to equip you with a solid foundation in Sightly, enhancing your skill set and enabling you to create more dynamic, efficient, and secure web experiences in AEM.

So, let’s dive in and unravel the capabilities of Sightly/HTL in Adobe Experience Manager!

II. What is Sightly in AEM?

Definition of Sightly/HTL

Sightly, which stands for “Sightly HTML Template Language,” is Adobe’s templating language introduced with Adobe Experience Manager (AEM) 6.0. It was created to offer a more intuitive and efficient way for developers to create and manage their AEM components. In recent iterations, Sightly has been rebranded as HTML Template Language (HTL), but the core concept remains the same. It’s a server-side template system that allows for the easy and secure rendering of HTML content within AEM.

HTL enhances the security of AEM applications by automatically handling common web vulnerabilities, such as Cross-Site Scripting (XSS). This is achieved through context-aware escaping, where the language understands the context in which a variable is used and escapes it accordingly. The goal is to provide a language that is not only powerful and flexible but also user-friendly and secure, even for those who may not be deeply versed in backend technologies.

The Evolution from Sightly to HTL

The transition from Sightly to HTL signifies Adobe’s commitment to evolving its technologies in line with modern web development practices. Originally introduced as Sightly, the language was envisioned to “sight” the HTML, meaning it was designed to look as close to HTML as possible. This approach made it easier for front-end developers to read and write AEM code without needing deep knowledge of Java, the primary language used in AEM.

As the language matured, Adobe rebranded Sightly to HTML Template Language (HTL) to better reflect its nature and capabilities. The rebranding also aimed to eliminate confusion with existing templating languages and emphasize its HTML-centric approach. Despite the name change, the principles and goals of the language remained unchanged. HTL continues to simplify and secure AEM development, allowing for more accessible and maintainable codebases.

Importance in AEM Development

The introduction of Sightly/HTL marked a significant shift in how AEM developers approach front-end development. Its simplicity and safety features have made it a preferred choice for creating robust and secure AEM websites and applications. The language allows for clear separation of concerns, where developers can focus on the HTML structure while the AEM backend takes care of the data management. This separation not only streamlines development but also enables a more collaborative environment where front-end and back-end developers can work more efficiently together.

Moreover, HTL integrates seamlessly with AEM’s component-based architecture. This integration means developers can create reusable components that are both scalable and maintainable, a vital aspect for large-scale enterprise websites. The ability of HTL to render server-side makes it a powerful tool in building dynamic web experiences, where content can be personalized and rendered on-the-fly based on user interactions and preferences.

In summary, Sightly/HTL is more than just a templating language; it’s a cornerstone of modern AEM development, enabling developers to build secure, efficient, and maintainable web applications that stand the test of time.

III. Setting Up Your Environment for Sightly

Setting up your environment correctly is the first step towards efficiently using Sightly/HTL in Adobe Experience Manager (AEM). This section will guide you through the basic requirements and provide a step-by-step process to set up Sightly for your AEM projects.

Basic Requirements for Working with Sightly in AEM

Before diving into the setup process, let’s ensure you have the necessary tools and software:

  1. Adobe Experience Manager (AEM): You need an instance of AEM, ideally the latest version, as it comes with HTL/Sightly support built-in. If you’re working within an organization, you might already have this set up. For individual developers, Adobe offers a developer version of AEM for learning purposes.
  2. Java Development Kit (JDK): AEM is a Java-based application, so having the latest version of JDK installed is crucial. Make sure you have JDK 8 or later installed on your machine.
  3. Integrated Development Environment (IDE): While you can technically write HTL code in any text editor, using an IDE like IntelliJ IDEA, Eclipse, or Adobe’s Brackets enhances your development experience with features like syntax highlighting and code completion.
  4. Maven: Apache Maven is used for building and managing projects in AEM. Ensure you have Maven installed and configured correctly.
  5. AEM Project Archetype: This is a Maven template used for creating standard AEM projects. It simplifies the process of setting up new AEM applications with recommended folder structures and dependencies.

Step-by-Step Guide to Setting Up Sightly

  1. Install and Configure AEM:
    • If you haven’t already, install AEM on your local machine. Follow Adobe’s official guidelines for installation.
    • Once installed, start the AEM instance. By default, AEM runs on localhost at port 4502.
  2. Configure Your IDE:
    • Install an IDE of your choice. Plugins or extensions for AEM development are available for popular IDEs and can assist in writing and debugging HTL code.
  3. Create a New AEM Project:
    • Use the AEM Project Archetype to create a new project. This can be done through Maven commands. For example, mvn archetype:generate with the appropriate parameters for the AEM version and archetype version.
    • Once the project is generated, import it into your IDE.
  4. Understanding the Project Structure:
    • Familiarize yourself with the standard structure of an AEM project. Key directories to note are /apps for your application code, /content for site content, and /conf for configuration settings.
  5. Writing Your First HTL Script:
    • Navigate to the HTL script location within your project, usually found under /apps/[project-name]/components/[component-name].
    • Start by modifying existing HTL files or creating new ones. Remember, HTL scripts are closely integrated with AEM components.
  6. Testing and Deployment:
    • After writing your HTL code, deploy your project to the AEM server using Maven. Use the command mvn clean install -PautoInstallPackage to build and deploy your project.
    • Test your HTL components by accessing them via the AEM authoring interface.
  7. Continual Learning:
    • As you explore HTL, refer to Adobe’s official documentation and community forums for guidance and best practices.

Setting up your development environment for Sightly/HTL might seem daunting at first, but it’s a critical step in ensuring that your AEM projects are efficient, scalable, and maintainable. With the environment ready, you can focus on leveraging the full potential of HTL in your AEM development projects.

IV. Core Concepts of Sightly in AEM Development

Understanding the core concepts of Sightly, now known as HTML Template Language (HTL), is crucial for efficient and effective AEM development. This section will delve into the syntax and principles of Sightly, along with how it stands apart from other templating languages.

Explanation of Sightly Syntax and Principles

Sightly/HTL is designed to be intuitive and straightforward, resembling HTML to a great extent, which makes it accessible even to those who are not deeply versed in programming. Let’s break down its key syntax and principles:

  1. HTML-Centric Design: At its core, Sightly is HTML with additional data-sly attributes. These attributes are used to add logic to the template, such as conditionals, loops, and variable declarations.
  2. Use-API: Sightly employs a ‘Use-API’ for backend logic. This allows developers to bind JavaScript or Java objects to their HTL files, keeping the business logic separate from the presentation layer. This separation enhances readability and maintainability.
  3. Context-Aware Escaping: One of Sightly’s standout features is its context-aware auto-escaping, which automatically applies the correct escaping method based on where a variable is used in the HTML. This feature significantly enhances security, particularly against Cross-Site Scripting (XSS) attacks.
  4. Data-Sly Attributes: The language introduces several data-sly attributes for various functionalities:
    • data-sly-test for conditional statements.
    • data-sly-list for iterating over collections.
    • data-sly-include and data-sly-resource for including other HTL components or resources.
    • data-sly-template and data-sly-call for defining and calling reusable templates.
  5. Expression Language: HTL uses an expression language for variable interpolation and simple logic. Expressions are enclosed in ${}. For instance, ${'Hello ' + world} would output ‘Hello world’ if the variable world is defined.

How Sightly Differs from Other Templating Languages

Sightly/HTL distinguishes itself from other templating languages in several key aspects:

  1. Security Focused: The auto-escaping feature in Sightly is a significant advancement in templating language design, prioritizing security by default. This approach reduces the burden on developers to manually handle potential security vulnerabilities.
  2. Clean Separation of Concerns: Sightly encourages a strict separation of the presentation layer from business logic. This is in contrast to some templating languages that allow embedding substantial amounts of logic directly in the templates, potentially leading to cluttered and hard-to-maintain code.
  3. Developer Accessibility: The HTML-like syntax of Sightly makes it more accessible to front-end developers who may not have extensive experience in backend programming. This contrasts with languages like JSP (JavaServer Pages) where deeper Java knowledge is often required.
  4. Integration with AEM: Being a part of the AEM ecosystem, Sightly is optimized for seamless integration with AEM’s features, such as components, dialogs, and workflows. This integration is not inherently available in other templating languages.
  5. Performance Optimizations: Sightly is designed with performance in mind, optimizing how templates are compiled and rendered in AEM. This results in faster page load times and an overall improved performance of the AEM sites.

Understanding these core concepts and differences provides a strong foundation for leveraging Sightly/HTL in AEM projects. Its unique blend of user-friendliness, security, and tight integration with AEM makes it a valuable tool for any AEM developer.

V. Creating Your First Sightly Template

Embarking on the journey of creating your first Sightly template is an exciting step in mastering AEM development. This section will guide you through the process of building a basic Sightly (HTML Template Language, HTL) template and provide best practices to follow.

Detailed Guide on Creating a Basic Sightly Template

1. Set Up Your AEM Project:

  • Ensure you have an AEM project set up as per the instructions provided in the previous sections.
  • Open your project in the IDE of your choice.

2. Create a New Component:

  • In AEM, templates are often associated with components. Begin by creating a new component in your AEM project.
  • Navigate to /apps/[your-project-name]/components/ and create a new folder for your component, say helloWorld.

3. Create the Sightly File:

  • Within your new component directory, create an HTML file. This will be your Sightly template. You can name it helloWorld.html.
  • Add the basic HTML structure to your file. Remember, Sightly templates are essentially HTML files with additional Sightly-specific attributes.

4. Add Sightly Logic:

  • Now, let’s add some Sightly elements. For example, to display a simple greeting message, you can use the ${} syntax to insert a variable.
  • Inside your helloWorld.html, add the following Sightly code:
  • <div data-sly-use.greet="${'com.example.HelloWorldModel'}"> <h1>${greet.message}</h1> </div>
  • This code uses the data-sly-use attribute to include a Java or JavaScript model (in this case, HelloWorldModel) and displays a message from this model.

5. Create the Java/JavaScript Model:

  • Create a new Java or JavaScript file in your component folder. This file will contain the logic for your message.
  • For Java, create a with a method that returns the greeting message. For JavaScript, a simple .js file with a similar functionality would suffice.

6. Test Your Component:

  • Deploy your changes to the AEM server.
  • Test your new component by adding it to a page within the AEM authoring environment and verify if the greeting message is displayed correctly.

Best Practices for Template Development

  1. Keep It Simple: Start with simple templates and gradually add complexity as you become more comfortable with HTL syntax.
  2. Separation of Concerns: Maintain a clear separation between your HTML (presentation) and Java/JavaScript (logic). Avoid embedding complex logic directly in your HTL files.
  3. Use Comments Wisely: While commenting is a good practice, over-commenting can clutter your code. Use comments to explain why something is done, not what is done.
  4. Consistent Naming Conventions: Use clear and consistent naming for files and variables to enhance readability and maintainability.
  5. Follow AEM Best Practices: Adhere to AEM development best practices, such as using client libraries for CSS and JavaScript, and leveraging AEM’s capabilities like dialogues and workflows.
  6. Test Thoroughly: Regularly test your templates in different scenarios and across various AEM environments.
  7. Stay Updated: Keep abreast of the latest developments in HTL and AEM. Adobe frequently updates AEM, and staying updated ensures you utilize the platform effectively.

Creating your first Sightly template is just the beginning. As you experiment and build more complex templates, you’ll gain a deeper understanding of the powerful capabilities of HTL in AEM.

VI. Integrating Sightly with AEM Components

Integrating Sightly, also known as HTML Template Language (HTL), with Adobe Experience Manager (AEM) components is a cornerstone of efficient AEM development. This section will explore how to use Sightly within AEM components and provide practical examples to illustrate this integration.

How to Use Sightly in AEM Components

1. Understanding AEM Components:

  • AEM components are reusable modules that form the building blocks of your AEM pages. They encapsulate both the logic and the presentation layer.
  • Each component typically includes a dialog for content authors to input data, a Java or JavaScript backend model, and an HTL file for rendering the content.

2. The Role of HTL/Sightly in Components:

  • HTL is primarily used in the presentation layer of an AEM component. It defines how the component’s content is rendered in the browser.
  • Sightly templates interact with the AEM Java Content Repository (JCR) to fetch and display content dynamically.

3. Basic Integration Steps:

  • Create a new component or open an existing one in your AEM project.
  • Inside the component folder, you’ll typically find an HTL file (e.g., myComponent.html). This is where you’ll write your Sightly code.
  • Use Sightly’s data-sly attributes to define how your component should display its content. For example, data-sly-list can be used to iterate over a list of items fetched from the JCR.

Examples of Sightly and AEM Components Integration

Example 1: Displaying a List of Items

  • Suppose you have a component designed to display a list of news articles.
  • In your HTL file, you could use: <ul data-sly-list.article="${properties.articles}"> <li>${article.title}</li> </ul>
  • This code iterates over a list of articles, assuming properties.articles is a collection provided by the backend model.

Example 2: Conditional Rendering

  • Consider a component that should display a message only if a certain condition is met.
  • You can utilize the data-sly-test attribute: <div data-sly-test="${properties.isLoggedIn}"> <p>Welcome back, ${properties.userName}!</p> </div>
  • This snippet checks if the user is logged in (properties.isLoggedIn) and, if true, displays a welcome message.

Example 3: Including Another Component

  • To include another component within your HTL file, use data-sly-resource or data-sly-include.
  • For example, to include a header component:htmlCopy code<div data-sly-include="/apps/myProject/components/header/header.html"></div>
  • This line includes the HTL file of the header component at the specified path.

By integrating Sightly within your AEM components, you can create dynamic, responsive, and interactive web experiences. This integration allows for the seamless rendering of content and provides a powerful way to build feature-rich AEM applications.

VII. Sightly Best Practices for AEM

Adopting best practices in Sightly, or HTML Template Language (HTL), is key to efficient and maintainable coding in Adobe Experience Manager (AEM). This section will cover essential tips and tricks for effective Sightly coding and highlight common pitfalls to avoid.

Tips and Tricks for Efficient Sightly Coding

1. Leverage Sightly’s Context-Aware Escaping:

  • Trust Sightly’s built-in context-aware escaping to handle potential security issues like Cross-Site Scripting (XSS). Avoid disabling this feature unless absolutely necessary.

2. Use Logic Appropriately:

  • While Sightly supports basic logic operations, heavy logic should be handled in the Java/JavaScript models, not in the HTL files. Keep the HTL as clean and presentation-focused as possible.

3. Optimize Use of Sightly Attributes:

  • Utilize data-sly-list and data-sly-repeat for iterating over collections efficiently. Understand the subtle differences between them (e.g., data-sly-repeat is more memory-efficient for large lists).

4. Make Use of Sightly’s Template and Call Mechanism:

  • Define reusable templates within HTL files using data-sly-template and invoke them with data-sly-call. This practice promotes code reusability and reduces duplication.

5. Externalize Strings for Internationalization:

  • Store display strings in dictionaries for localization and internationalization. Use ${'string' @ i18n} syntax for fetching localized strings.

6. Efficiently Manage Client Libraries:

  • Include CSS and JavaScript efficiently using AEM’s Client Library system (cq:ClientLibraryFolder). It helps in better managing and loading resources.

7. Test Driven Development (TDD):

  • Adopt a TDD approach for AEM development. Writing tests for your Java classes and JavaScript files ensures robustness and maintainability.

Common Pitfalls and How to Avoid Them

1. Overusing HTL for Logic:

  • Avoid writing complex business logic directly in HTL. This not only makes the code difficult to read but also goes against the principle of separation of concerns.

2. Ignoring Component Reusability:

  • Design your components with reusability in mind. Avoid creating very specific components that can’t be reused across different parts of the application.

3. Hardcoding Paths and Strings:

  • Avoid hardcoding paths and strings directly in HTL. Use AEM’s dialog and design dialog features to make components flexible and configurable by content authors.

4. Neglecting Performance Optimization:

  • Be mindful of performance. Excessive use of expensive operations like data-sly-resource and unnecessary complex queries can impact page load times.

5. Bypassing Security Features:

  • Do not disable Sightly’s auto-escaping without a valid reason. Disabling it without understanding the implications can open up security vulnerabilities.

By adhering to these best practices and being aware of common pitfalls, you can ensure that your Sightly code is not only efficient and secure but also maintainable and scalable. This approach is essential for building professional and high-quality AEM websites and applications.

VIII. Advanced Sightly Features and Techniques

As you grow more comfortable with Sightly (HTML Template Language, HTL) in Adobe Experience Manager (AEM), exploring its advanced features can significantly enhance your development capabilities. This section provides an overview of advanced Sightly features and discusses how to leverage them in complex AEM projects.

Overview of Advanced Sightly Features

1. Display Contexts and HTML Output:

  • Sightly offers various display contexts for controlling HTML output, such as html, attribute, javascript, etc. Understanding and using these contexts correctly can ensure proper rendering and enhance security.

2. Use-API Extensions:

  • Sightly’s Use-API can be extended with custom Java or JavaScript objects, allowing for more sophisticated back-end integrations and logic implementations.

3. Sightly Java API:

  • For complex logic that cannot be efficiently handled in JavaScript, Sightly provides a Java API. This API can be used to create more advanced business logic layers, tightly integrated with Sightly templates.

4. Sling Models:

  • Sling Models in AEM provide an elegant way to bind Java objects to Sightly templates. They offer a cleaner and more annotation-driven approach compared to traditional JSP JavaBeans.

5. Client-Side Rendering (CSR):

  • For dynamic client-side interactions, Sightly can be combined with client-side frameworks like Angular or React. This combination allows for the creation of highly interactive and responsive user interfaces.

Leveraging Advanced Features in Complex AEM Projects

1. Custom Display Contexts for Enhanced Security:

  • In scenarios where standard auto-escaping does not suffice, use custom display contexts to handle special HTML rendering cases, ensuring both functionality and security.

2. Extending Use-API for Complex Back-End Logic:

  • Utilize the Use-API to encapsulate complex back-end logic in Java/JavaScript, keeping your HTL files clean and focused on presentation.

3. Advanced Business Logic with Java API:

  • Implement complex business logic with the Sightly Java API, especially in scenarios where JavaScript might fall short in terms of performance or capabilities.

4. Streamlining Data Binding with Sling Models:

  • Employ Sling Models for an efficient and maintainable way to bind back-end data to your HTL templates, especially in projects with complex data structures.

5. Integrating CSR for Dynamic UIs:

  • In projects requiring dynamic, real-time content updates, integrate client-side rendering frameworks with Sightly. This allows leveraging AEM’s content management capabilities while providing a dynamic user experience.

6. Optimize Performance for Large Scale Projects:

  • In large-scale projects, be mindful of performance. Utilize AEM’s caching mechanisms and be cautious with resource-intensive operations in your HTL files.

7. Continuous Learning and Experimentation:

  • The field of web development is always evolving. Stay updated with the latest advancements in HTL and AEM, and don’t hesitate to experiment with new techniques and integrations.

By mastering these advanced features and understanding how to apply them in complex projects, you can significantly enhance the functionality, performance, and security of your AEM applications. Advanced Sightly development opens the door to creating sophisticated and robust web experiences that meet the evolving needs of modern digital landscapes.

IX. Resources for Further Learning

Continuing your learning journey in Sightly (HTML Template Language, HTL) and Adobe Experience Manager (AEM) is essential for staying updated and honing your skills. This section lists recommended books, online resources, and communities that can help you deepen your knowledge and stay abreast of the latest developments.

  1. “Adobe Experience Manager: Classroom in a Book” by Ryan D. Lunka
    • Offers a comprehensive introduction to AEM, covering fundamental concepts, including sections on Sightly/HTL.
  2. “Developing with Adobe Experience Manager” by Daniel Klco
    • A more technical dive into AEM, suitable for developers who want to deepen their understanding, including advanced topics in HTL.
  3. “Pro AEM as a Cloud Service” by Sreekanth Choudry Nalabotu and Sreenivas Munnangi
    • Focuses on AEM as a Cloud Service, providing insights into modern AEM development practices, including HTL usage.

Online Resources

  1. Adobe Official Documentation
  2. AEM Tutorials and Blogs
  3. Online Courses and Webinars
    • Platforms like LinkedIn Learning, Udemy, and Pluralsight offer courses on AEM, catering to various expertise levels.


  1. Adobe Experience League Community
  2. Stack Overflow
    • A vast repository of AEM and HTL related questions and answers. Tag your queries with ‘aem’ or ‘sightly’ for specific help.
  3. GitHub Repositories
    • Explore open-source AEM projects on GitHub to understand how others are using HTL in real-world scenarios.

Staying Updated with Sightly/HTL Developments

  1. Follow Adobe Release Notes
    • Regularly check Adobe’s release notes for the latest updates and features in AEM and HTL.
  2. Subscribe to AEM Blogs and Newsletters
    • Stay subscribed to blogs and newsletters from AEM thought leaders and Adobe itself for insights and updates.
  3. Participate in Forums and Webinars
    • Engage in forums and attend webinars to stay in touch with the latest trends and best practices.
  4. Networking with Peers
    • Connect with fellow AEM developers through LinkedIn groups, local meetups, and conferences.

By leveraging these resources and actively engaging with the AEM community, you can continue to grow your expertise and stay at the forefront of the rapidly evolving field of AEM development.


As we conclude this comprehensive introduction to Sightly (HTML Template Language, HTL) in Adobe Experience Manager (AEM), let’s summarize the key takeaways:

  1. Understanding Sightly/HTL: We explored the basics of Sightly, its evolution into HTL, and its significance in AEM development.
  2. Setting Up Your Environment: We walked through the essential steps to set up your development environment for Sightly in AEM.
  3. Core Concepts: We delved into the core concepts of Sightly, understanding its syntax and how it differs from other templating languages.
  4. Creating and Integrating Templates: We learned how to create a basic Sightly template and integrate it with AEM components, a fundamental skill in AEM development.
  5. Best Practices and Advanced Techniques: We covered best practices for efficient coding in Sightly and explored advanced features for complex AEM projects.
  6. Resources for Further Learning: Finally, we listed valuable resources for further enhancing your knowledge and skills in AEM and Sightly/HTL.

Preview of What’s Next in the AEM 101 Series

In our upcoming posts, we will dive deeper into other aspects of AEM development. Look forward to in-depth discussions on topics such as AEM Workflows, Personalization in AEM, and Integrating AEM with Other Adobe Solutions. These upcoming posts will aim to expand your knowledge and expertise, helping you become a more versatile and proficient AEM developer.

Your feedback and participation are invaluable to us. I encourage you to comment below with your thoughts, experiences, or queries about using Sightly in AEM. If you found this guide helpful, please feel free to share it with your peers or anyone interested in AEM development.

Don’t forget to explore the previous posts in our AEM 101 series to build a comprehensive understanding of Adobe Experience Manager. Each post is designed to guide you through different facets of AEM, equipping you with the knowledge and skills needed for effective AEM development.

Stay tuned for more insightful content, and let’s continue to grow as a community of AEM enthusiasts and professionals!

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