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What Is an API (And How REST Makes Frontend-Backend Communication Work)
January 6, 2026 · 5 min read★ Featured
APIs are the secret sauce that let your frontend talk to your backend. Here's a plain-language guide to how they work and why they matter for Wagtail projects.
In my last post, I talked about decoupling frontend and backend. One piece I didn’t explain in detail is how the two actually communicate. That’s where APIs come in.
APIs (Application Programming Interfaces) are the bridge that allows your frontend to request data from your backend-like content stored in Wagtail and display it anywhere, from a website to a mobile app.
Let’s break down what that really means.
What Is an API?
Think of an API like a waiter in a restaurant.
API at the Restaurant
Think of an API like a waiter in a restaurant.
- You (the frontend) sit at the table with a menu (the API documentation).
- The waiter (the API) takes your order (request) to the kitchen (backend) and brings back your food (response).
- You don’t see the kitchen or know how it prepares the food—you just get what you asked for.
APIs let different systems talk to each other without knowing each other’s inner workings. This is especially useful when you want your backend to serve multiple frontends: web, mobile, or even other third-party applications.
REST APIs in a Nutshell
Most web APIs follow the REST (Representational State Transfer) principles. REST is a set of conventions that make APIs predictable and easy to use.
Here's the idea:
- Everything is a resource: pages, blog posts, images, users.
- Each resource has a unique URL.
- You use HTTP methods to interact with resources:
- GET → Retrieve data
- POST → Create something new
- PUT/PATCH → Update something
- DELETE → Remove something
For example, if your Wagtail backend manages blog posts, a REST API might look like this:
GET /api/posts/→ Get all postsGET /api/posts/123/→ Get a single postPOST /api/posts/→ Add a new postPATCH /api/posts/123/→ Edit a postDELETE /api/posts/123/→ Delete a post
The backend returns JSON, a structured data format the frontend can read. Then, your frontend (React, Next.js, Vue, etc.) uses that data to render pages.
“APIs let different systems talk to each other without knowing each other’s inner workings. This is especially useful when you want your backend to serve multiple frontends: web, mobile, or even other third-party applications.”
Why REST Makes Life Easier
REST APIs are everywhere because they solve a few key problems:
1. Separation of Concerns
The frontend and backend can evolve independently. Frontend developers don’t need to touch Wagtail templates or Python code, they just consume data. Backend developers don’t care how the frontend displays it, they just serve JSON.
2. Multiple Frontends, One Backend
Your Wagtail content can power a website, mobile app, or even an IoT device simultaneously. The API is the single source of truth.
3. Predictable and Standardized
Once you know REST conventions, you can consume any REST API even outside your project. URLs, methods, and responses are standardized.
4. Enables Decoupled Workflows
You can integrate previews, live updates, and automated deployments. For example, when you update content in Wagtail, the API delivers it instantly to your frontend without extra rendering logic.
How Wagtail Exposes Content via API
Wagtail comes with a built-in REST API (API v2) that makes it easy to serve pages and content as JSON. This is the bridge your frontend uses to fetch content without touching templates.
At a high level:
- Wagtail provides endpoints for pages, images, and collections.
- Each endpoint returns JSON data representing your content.
- The frontend can request a list of pages, a single page, or even filtered content.
Enabling API v2 in your project is straightforward. In your urls.py:
from wagtail.api.v2.router import WagtailAPIRouter
api_router = WagtailAPIRouter('wagtailapi')
urlpatterns = [
path('api/v2/', api_router.urls),
]
After this, your pages become accessible at URLs like /api/v2/pages/, ready to be fetched by your frontend.
The beauty of API v2 is that it works out-of-the-box for standard Wagtail pages, so you don’t need to write extra code unless you want custom fields or behavior.
Trade-Offs to Keep in Mind
APIs aren’t magic. They come with their own challenges:
- Authentication & Permissions: You must secure endpoints so only authorized users can create or edit content.
- Versioning: If the API changes, old frontends might break.
- Extra Layer of Complexity: Debugging API calls adds steps compared to traditional template rendering.
For small sites or content-driven blogs, the extra complexity might not be worth it. But for a decoupled architecture or multi-platform strategy, APIs are essential.
Key Takeaways
- APIs are bridges between frontend and backend.
- REST APIs follow simple, predictable conventions (resources, URLs, HTTP methods).
- Wagtail API v2 makes it easy to expose pages and content as JSON.
- Decoupling via API gives you flexibility, but adds complexity.
Understanding APIs is the first step to fully leveraging Wagtail in a modern frontend workflow. Once you get this, building a React or Next.js frontend that consumes Wagtail content becomes almost second nature.
What's Next
After grasping REST APIs, the next piece of the puzzle is:
- Introduction to Wagtail Project structure - Basics to organize the project
- How Wagtail’s StreamField - Architecture that enables flexible content
- Modular content blocks combine with APIs - Solution to deliver dynamic, reusable frontend components
From there, we’ll dive into content modeling patterns, API best practices, and how to keep your decoupled stack maintainable.