What I’ve Liked About Trying Svelte as an Ember Dev
11/17/2025
1. Introduction
I've worked with numerous frontend frameworks over the years—Angular, Vue, Next.js—but I kept coming back to Ember.js. With over a dozen years of experience in the Ember ecosystem, I've seen it evolve from its early days to the robust framework it is today. The focus on migration and support is unparalleled; the number of apps that have upgraded and stayed maintained over a decade is a testament to the Ember community's principle of building shared resources. I've worked in more than a half dozen Ember apps, spending years working in each, starting from Ember version 1.
The Ember community is racing headfirst towards a Vite-based setup, and my curiosity about other Vite-powered solutions led me to SvelteKit. I'd been hearing the buzz about Svelte for some time, and with my personal website due for a refresh, it felt like the right time to dive in. The site itself was a small Ember app, with its most complex part being a playable Sudoku game—a perfect candidate for a controlled experiment.
My thesis is simple: for an experienced Ember developer, SvelteKit feels comfortably familiar in many ways, while also improving on several long-standing pain points. It’s a transition that feels less like a departure and more like a logical next step.
2. What Feels Familiar
Svelte's unique approach, often described as a "disappearing framework" because it compiles away into highly optimized vanilla JavaScript at build time (rather than shipping a large runtime), aligns surprisingly well with the structured, convention-over-configuration world of Ember.
Routing
Ember’s router-first approach, where routes own their data, has always provided a predictable mental model. SvelteKit’s filesystem-based routing achieves a similar result with less ceremony. Each route directory can have a +page.js or +page.server.js that acts like an Ember route.js file, responsible for fetching data. This creates a clear and intuitive connection between the URL and the data that powers the page, something any Ember developer will appreciate.
HTML Templating Feels Like Modern Handlebars
Svelte’s templating syntax immediately feels like a more powerful version of Handlebars. Expressions are inline, conditional logic with {#if} and {:else}, and looping with {#each} are all direct parallels. The single-file component structure, where the template, script, and style live together, mirrors the ergonomics of an Ember component, but with the added benefit of colocation. The transition is seamless, and the ability to use standard JavaScript expressions without helpers is a welcome improvement.
Scoped CSS vs. ember-css-modules
Component-scoped styling has been a best practice in Ember for years, often accomplished with ember-css-modules. Svelte offers this out of the box, with zero configuration. Every <style> tag in a Svelte component is automatically scoped to that component, preventing style bleed and making maintenance a breeze. It’s the same pattern, but simpler and more integrated.
Testing
Ember's out-of-the-box testing story is comprehensive, with its three-pronged approach of acceptance, component, and helper tests. SvelteKit, with its Vitest integration, offers a lighter, more modular setup that still feels robust. Writing predictable, isolated tests for components or utility functions is just as straightforward, and the leaner configuration makes it feel simpler and faster.
For end-to-end testing, SvelteKit's integration with tools like Playwright provides a similar experience to Ember's acceptance tests—both test the application from the user's perspective, simulating real interactions and verifying full user workflows. The main difference is that Playwright offers more flexibility in running tests across different browsers and environments, though the core philosophy of testing complete user journeys remains the same.
Live Reload
Ember CLI’s live reload has always been solid, but SvelteKit’s Hot Module Reload (HMR) via Vite is a game-changer for stateful applications. The ability to tweak a component’s logic or styles without losing its current state makes iterative development significantly faster and smoother. It reduces friction and keeps you in the flow.
3. Where Svelte Improves On Ember
While the familiar patterns make for a comfortable transition, SvelteKit truly shines in the areas where it streamlines or reimagines established web development workflows.
E2E Testing Outside the Browser
With tools like Playwright integrated from the start, SvelteKit encourages a more flexible and lightweight approach to end-to-end testing. Running tests in a Node.js environment, without always needing to spin up a full browser, simplifies the testing of large, stateful applications and makes for a faster, more reliable CI process.
One major advantage over Ember's acceptance tests is that you can test against a real backend. In Ember, acceptance tests run entirely in the browser, which means the entire backend API must be mocked in client-side JavaScript—often using libraries like Mirage. This creates a significant maintenance burden, as you're essentially maintaining a parallel implementation of your API. With SvelteKit and Playwright, you can run tests against actual server routes and endpoints, reducing duplication and ensuring your tests reflect real-world behavior.
Hot Module Reload (HMR)
As mentioned, HMR is a significant step up from traditional live reload. By preserving component state during code changes, it eliminates the tedious process of re-navigating and re-triggering UI states just to see the effect of a small change. This is a massive quality-of-life improvement that reduces friction and accelerates the development feedback loop.
App Structure: More "Pod-Like"
SvelteKit's file-based routing naturally encourages a "pod-like" structure, where the template, code, and styles for a route are all colocated in the same directory. This modular, self-contained approach keeps related files together, making the codebase easier to navigate and reason about. It mirrors the spirit of Ember’s "Data Down, Actions Up" (DDAU) philosophy but enforces it through a simple, intuitive file structure.
Integrated Server Side Rendering + Client Side Rendering
This is perhaps the most significant departure from the traditional Ember model. With SvelteKit, server-side logic is not a separate concern. Server routes, API endpoints, and form actions can be colocated with their corresponding frontend components. This allows for unified validation logic that runs on both the server and the client, a clear separation between the UI and its API, and proper use of HTTP response codes—a long-standing tradeoff in the single-page application world.
Server Rendering + Pluggable Server Strategy
FastBoot brought server-side rendering to Ember, but it notably never provided rehydration, meaning the client-side application had to re-bootstrap entirely. SvelteKit, in contrast, makes SSR a first-class citizen with a more flexible, adapter-based strategy and seamless rehydration. Whether you're deploying to Node.js, Cloudflare Workers, Vercel, or another target, you run the same code with minimal configuration changes. Combined with route-based code splitting and tree-shaking out of the box, it delivers a highly optimized user experience with a developer-friendly workflow.
4. Closing / Reflection
My journey from Ember to SvelteKit has been both comfortable and enlightening. The familiar patterns in routing, templating, and testing made for a smooth transition, while the modern ergonomics and integrated features felt like seeing some of Ember’s best ideas fully realized in a leaner, more modern package.
For any long-time Ember developer curious about what else is out there, SvelteKit offers a compelling answer. It proves that the cross-pollination of ideas between frameworks is not just a theoretical exercise, but a practical way to push the web forward. It's a reminder that even after a decade with one framework, there are always new and energizing ways to build for the web.