Svelte Updates & Release Notes

SvelteKit 3 is here! Check out the announcement post for the highlights, then run sv migrate to handle most of the upgrade for you. sv itself hit 1.0 on the same day, making the community add-on API official. Below you’ll find the last round of changes that landed before 3.0 - adapter API updates, zero-config deploys to Render and a few final breaking changes.

Svelte Summit is also back for Svelte’s 10th birthday! It’s happening in Ljubljana on November 19-20 with talks from Rich Harris, Elliott Johnson, Paolo Ricciuti, Stanislav Khromov, pngwn and more. In-person and virtual tickets are available at sveltesummit.com.

Svelte itself had a quiet month - 5.57.1 is all bug fixes and parser performance work. Per usual, there’s still plenty in the showcase... so let’s dive in!

What’s new in SvelteKit 3

• Adapters now receive the Svelte config as a function argument when adding Vite plugins (3.0.0-next.27, #16986)
• Adapters can override getRequest and setResponse during vite dev and vite preview, so local requests behave more like the target platform (3.0.0-next.27, Docs, #16753) …

Version 3.0 of SvelteKit, the official application framework for Svelte, is now available.

If you’ve used earlier versions of SvelteKit, everything will feel very familiar — it’s the same framework with a little more polish, a little more type safety, and a little less junk. We’ve made migration as seamless as we can with the sv migrate command...

npx sv migrate sveltekit-3 --tasks all --confirm

...which will automatically migrate as much of your codebase as possible, and generate a TODO list for everything else. (If you’re agentically inclined, your robot friends will make short work of it.)

To create a new app, run sv create:

npx sv create my-new-app

As with any major version bump there are a handful of breaking changes to be aware of, which are covered in the migration guide (or, more briefly, in the recent release candidate announcement).

Quick highlights:

• configuration now lives in vite.config.ts instead of svelte.config.js
• the $lib alias is now #lib, making use of standard subpath imports
• environment variables are more powerful and easier to use
• service workers are less boilerplatey
• error handling is improved across the board …

This month, Svelte 5.57 shipped with new SvelteMap methods and a few quality-of-life additions while SvelteKit 3 got closer to the finish line with its Release Candidate.

The sv CLI also got a new ai-tools add-on that replaces the old mcp one, and sv@next now ships a task-based sveltekit-3 migration for existing apps.

Let’s dive a bit deeper!

What’s new in Svelte

• SvelteMap now has getOrInsert and getOrInsertComputed methods for the common “read or initialize” pattern (5.57.0, Docs, #18728)
• createContext now returns a third has function so you can check whether a context has been set without triggering the get error (5.57.0, Docs, #18472)
• <select> now supports the defaultValue attribute, so the select reverts to that value on form reset (5.57.0, #18591)
• svelte/server now exports the RenderOutput, SyncRenderOutput, Csp and Sha256Source types for typing server render output and CSP sources (5.57.0, #18648)

For the full list of patches and bug fixes, see the Svelte CHANGELOG. …

SvelteKit 3 is now in the Release Candidate phase. If all goes well — meaning that people like you try it out and find that it works as expected — we will follow it up with a stable release in the near future, with no further breaking changes.

But there are some breaking changes since SvelteKit 2. We’re taking advantage of this release to prune some of the weeds in the codebase and lay the groundwork for SvelteKit’s continued evolution, more on which below.

To migrate an existing app, you can use the next version of sv migrate:

npx sv@next migrate sveltekit-3 --tasks all --confirm

This will automatically migrate as much of your code as possible. For everything else, it will generate a TODO list for you (or your clanker of choice) to work through. Wherever possible, SvelteKit will print useful diagnostic warnings and errors if you try to run code that hasn’t yet been updated.

To create a new app, run sv create:

npx sv@next create my-new-app

What’s changed?

For the full list of changes, consult the migration guide over on next.svelte.dev which is where the SvelteKit 3 documentation will live until the stable release. Most changes are fairly minor, but a few are worth calling out: …

The biggest news this month is the first @next releases of SvelteKit 3. Thirteen preview versions shipped in July: previewing new $app/manifest and $app/service-worker modules, improved API availability and type checking in service workers, tracing out of the experimental namespace, shallow routing baked into goto and a lot more. It’s a prerelease, but it’s worth trying out to see what’s coming to SvelteKit!

Alongside the preview releases, the stable line kept moving with submitted on remote forms and a new home for defineEnvVars. The language tools also picked up zero-config +error.svelte props so error pages get their page and error types with no extra setup.

And, in case you missed it, Svelte Summit Ljubljana 2026 is happening November 19-20, with a workshop day on November 18, the day before the summit. Save the date!

What’s new in SvelteKit

• Remote forms now expose a submitted property so you can react to the moment a form is submitted without waiting for the response (2.69.0, Docs, #14811)
• defineEnvVars has moved from @sveltejs/kit to @sveltejs/kit/env so environment helpers live in a dedicated subpath (2.70.0, Docs, #16378) …