APIs and SDKs play a crucial role in streamlining the development process when integrating third-party tools or email/page building software.
While both are essential, they serve different purposes—one enabling communication between applications and the other providing a comprehensive toolkit for seamless integration.
Understanding the difference between APIs vs. SDKs helps developers make informed decisions about when to use each. In this guide, we’ll discuss their definitions, key differences, and use cases.
We’ll also show you how Unlayer’s REST API and JavaScript SDK simplify embedding a powerful no-code builder into your existing platform.
Let’s dive in! 🚀
What Is an API?
An Application Programming Interface (API) is a set of programming instructions that allows different software applications to communicate with each other.
APIs define how requests and responses within the applications should be structured, enabling seamless data exchange between systems without exposing the underlying code.
How do APIs enable communication?
They act as messengers, allowing one application to request specific data or services from another.
Think of them as waiters in a restaurant:
💡 Cloud-based services act as external providers—just like a restaurant might source desserts from a bakery instead of making them in-house. Instead of storing and processing everything locally, applications use APIs to fetch data or services from the cloud.
Examples of APIs are:
A payment gateway API (e.g., Stripe, PayPal) lets e-commerce platforms process transactions.
A social media API (e.g., Twitter, Facebook) enables third-party apps to post updates or fetch user data.
Unlayer’s API: Simplifying email & page design
Another example is Unlayer’s REST API that allows developers to connect this platform with their own storage or backend systems. Consequently, this lets the end-users, like the marketing or design team, to load, save, and manage their content from within the host application.
In short, it gives developers the liberty to:
✅ Load existing email and page designs into the editor.
✅ Save user-created designs programmatically.
✅ Export HTML and JSON versions of designs for further customization or sending.
What Is an SDK?
A Software Development Kit (SDK) is a collection of tools, documentation, libraries, and APIs that help developers integrate specific functionalities or builders more efficiently into their host applications.
Instead of building features or email/page building tools from scratch, developers can use SDKs to embed pre-built solutions, speed up development, and ensure seamless integration and compatibility with their applications.
How do SDKs simplify development?
SDKs provide everything you need to integrate a solution into your existing application, including:
✅ Pre-built libraries – Ready-to-use code for quick implementation.
✅ APIs – Interfaces to interact with external services.
✅ Documentation & Examples – Guidelines to help developers integrate and customize functionality.
Real-world example: Unlayer’s SDK for email & page building
Unlayer provides a JavaScript SDK so you can embed and integrate Unlayer’s drag and drop email and page builder into any application. Instead of coding an entire design editor from scratch, you can:
Embed a pre-built editor with just a few lines of code.
Customize the UI and other features to match your platform’s branding.
Give end-users full design flexibility while maintaining backend control.
Bonus tools: Plugins for seamless integration
To make the integration process easier for developers, Unlayer also has plugins for popular JavaScript frameworks, like:
These act as alternatives to SDK, allowing developers to embed Unlayer into their application when using the above-mentioned specific platforms.
Customization options: An essential part of an SDK
A well-integrated builder is something that should align with your application’s look, feel, usability, and workflow requirements. Developers should be able to fine-tune its appearance, behavior, and functionality to ensure a seamless experience for end-users.
1. Visual customization to match the builder’s look and feel
Customizing the builder’s interface can easily help you maintain brand consistency with your platform’s design.
✅ Themes & layouts – Choose from pre-built themes (light/dark modes) or define custom theme objects to align with your brand’s style.
✅ Custom CSS & JS – Modify the editor’s appearance and behavior with additional scripts and styles to fit specific design needs.
✅ Design tweaks – Make changes to the builder’s UI elements to enhance the user interface for an effortless editing experience.
2. Editor behavior to optimize user experience
In this section, developers can configure how the builder operates to make it intuitive and user-friendly:
✅ Auto select on drop – Automatically selects a tool when it’s placed in the editor for faster editing.
✅ Confirm on delete – Prevents accidental content deletion by enabling confirmation prompts.
✅ Undo/redo actions – Allows users to revert or repeat changes for a seamless editing workflow.
✅ Preview & responsive controls – Ensures designs look perfect across devices by enabling previews and responsive adjustments.
3. Content settings to ensure design consistency
Configurable content settings help developers maintain basic content structure while allowing end-users creative flexibility:
✅ Default body values – Set background colors, fonts, and preheader text for a uniform look.
✅ Page anchors – Create internal links within designs to improve navigation.
✅ Custom column sizes & row limits – Define layout constraints to keep designs structured.
4. Custom tools to extend the editor’s functionality
Every business has unique needs, and to reach its full potential, it requires the right set of tools.
That’s why we offer you the ability to seamlessly integrate fully functional custom tools into the editor’s interface. This gives you the flexibility to create unique design components that truly reflect your brand.
Unlike built-in tools, these give you complete control over the email/page builder's appearance, behavior, and interactivity.
5. Custom blocks to provide reusable design components
And the best part? You can also add your own custom blocks to the editor so the emails or landing pages your end-users create are always aligned with their specific goals and vision.
Whether they need a Call-to-Action, image block, or text section, they just need to design it once. Then, they can simply drag and drop these elements into their template for future use.
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Start designing with a powerful drag-and-drop builder
Key Differences Between APIs & SDKs
Feature | API | SDK |
Definition | Interface for app communication | Toolkit with APIs, libraries, and docs |
Use Case | Data exchange & automation | Embedding & simplifying development |
Example | Fetching data from a weather service | Mobile app SDK for push notifications |
Unlayer Example | Exporting email HTML via API | Embedding an email builder via SDK |
When to Use an API vs. an SDK?
APIs and SDKs serve different purposes in software development, but they also work hand-in-hand to improve the overall developer experience.
However, choosing the right one depends on whether you need to enable communication between systems (API) or embed a fully functional tool with a ready-to-use interface (SDK).
Let’s break it down further for you.
Use an API when
✅ You need to interact with external/host software/services
APIs serve as a bridge between applications, allowing smoother data exchange and automation.
✅ You want to automate processes
APIs streamline backend operations, whether fetching user-generated templates or email lists, saving email designs, or triggering email campaigns. This ultimately ensures that content is managed dynamically across platforms without leaving the host application.
✅ Developers and API needs
For internal tools – Developers focus on embedding Unlayer’s email/page builder in a way that meets the needs of internal teams. This often involves advanced API integration for internal storage, content approval workflows, or version control.
For end-user-facing platforms – In this case, developers need to consider factors like ease of use, role-based access for different user types, and data management for saving and retrieving content created by end-users.
Use an SDK when
✅ You want to embed a pre-built tool seamlessly
SDKs come with all the essential components, such as UI, docs, libraries, and APIs, to integrate functionality into your platform without breaking the bank or building a tool from scratch.
✅ You need a developer-friendly UI with customization options
SDKs provide a smooth front-end experience with drag and drop functionality while still allowing developers to tailor the interface and features (with advanced customization options) to match their brand’s requirements.
✅ Two key use cases for Unlayer’s SDK
Embedding Unlayer for internal teams – Businesses integrate Unlayer’s no-code email/page builder into their internal platforms, enabling teams like marketing or communications to create content such as emails, landing pages, popups, newsletters, and internal memos. In this scenario, Unlayer is used as an internal tool to streamline content creation.
Using Unlayer for public-facing platforms – Companies embed Unlayer into their SaaS or e-commerce platforms as a white-label solution.
Example: A platform like Shopify can integrate Unlayer’s drag and drop builder to allow merchants to create emails, signup forms, or product launch pages.
Example: An email marketing SaaS platform like Mailchimp can use Unlayer’s editor to help end-users build custom landing pages alongside their email campaigns.
Wrapping It Up
By now, you should have a clear understanding of APIs and SDKs. And choosing the right one depends on your development needs. For instance, if you just need to fetch or send data, an API is your go-to.
If you’re looking to embed a feature-rich tool with minimal development effort, an SDK is the way to go.
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