Svelte

Remote functions • Docs • Svelte Remote functions • Svelte documentation

SvelteKit remote functions are now available under an experimental flag. Docs here: svelte.dev/docs/kit/rem...

long overdue but we made the SvelteKit router more type-safe. docs for `resolve(...)` and `asset(...)` at svelte.dev/docs/kit/$ap...

now available for your on-demand viewing pleasure

Asynchronous Svelte · sveltejs svelte · Discussion #15845 This is a long document; get yourself a cup of tea. tl;dr You can now use the await keyword in Svelte — in your <script>, inside $derived expressions, and in your markup — by installing the async b...

Async Svelte is coming! github.com/sveltejs/sve...

Bringing Svelte Summit to the whole community We’re sponsoring the release of talks from Barcelona, starting this weekend

For those of you who have been wondering if and when the videos of Svelte Summit 2025 Barcelona will be freely available, we just published a blog post about it: svelte.dev/blog/svelte-...

XSS via tracked search_params ### Summary Unsanitized search param names cause XSS vulnerability. You are affected if you iterate over all entries of `event.url.searchParams` inside a server `load` function. Attackers can ex...

We just published an advisory for CVE-2025-32388, a moderate severity XSS vulnerability in SvelteKit. Please update to `@sveltejs/kit@2.20.6`.

The vulnerability affects applications that iterate over all search parameters inside a server `load` function. More details in the advisory 👇

TypeScript! • Playground • Svelte Web development for the rest of us

you can now use .ts files in the playground:

svelte.dev/playground/7...

caveat: only supports erasable syntax (www.typescriptlang.org/docs/handboo...). under the hood this uses bloomberg.github.io/ts-blank-spa...

(note that typechecking/intellisense are TODO)

If you're using SvelteKit (or Svelte+Vite without SvelteKit) then we recommend updating your Vite version.

Note that the vulnerability only exists if you're doing `vite dev --host` (or `server.host: true`) on an untrusted network, which you're probably not. But update anyway

A screenshot of https://svelte.dev/playground/3de3a4446cd14bad884ea05fbd35363a?version=5.25.0 showing the new 'writable derived' feature

As of @svelte.dev 5.25 you can temporarily override a derived value, which is very handy for optimistic UI

• demo svelte.dev/playground/3...
• docs svelte.dev/docs/svelte/...

last chance to grab tickets at the lower price!

PSA for @svelte.dev users: we're planning to change how effect teardowns work to eliminate a common gotcha that affects signal-based frameworks. If the new behaviour would create problems for you, please let us know!

github.com/sveltejs/sve...

Now that speakers have been selected we want to share with you our line-up for Svelte Summit Spring 2025! We will host 16 talks across different topics during the two day conference. In addition, @mainmatter.com will also host a workshop. More details on www.sveltesummit.com

New in Svelte: A way to create a unique ID that is stable across client and server svelte.dev/docs/svelte/...

in case you missed it: the SvelteHack winners are up! many thanks to everyone who took part, and kudos to these outstanding projects in particular 👇

We've just sent out emails to everyone who submitted a proposal! Please read it carefully. See you at Svelte Summit Spring 2025!

....and that's a wrap for this year. Thanks for following along, everyone! There's a bunch of stuff that we didn't quite manage to squeeze in this month, so keep an eye out in 2025 for more good things.

Merry Christmas to all who celebrate!

screenshot of svelte.dev/playground showing the new `class` attribute handling

Day 24 — Svelte now handles `class` attributes with github.com/lukeed/clsx. Much more powerful than the `class:` directive, but since this is Svelte you still get dead code elimination of unused styles!

🎁 docs svelte.dev/docs/svelte/...
🎁 demo svelte.dev/playground/6...

fix: add CSP hashes/nonces to inline styles when using by Rich-Harris · Pull Request #13232 · sveltejs/kit I forgot to account for CSP when adding inline styles for bundleStrategy: &#39;inline&#39;. No test in this PR because there are no tests for bundleStrategy: &#39;inline&#39; anyway, and life is to...

for scripts, yes. i forgot to account for styles though — good catch! opened github.com/sveltejs/kit...

screenshot of svelte.dev/playground showing the new 'download app' option

Day 23 — you can now download your playground creations as SvelteKit apps! It'll even include any dependencies you've imported

🎁 svelte.dev/playground

okay, kinda fixed mobile — you can tap the edges of the screen to control the snek. it'll do for now! going to go and do some christmas shopping

Downloadable Snake game built with SvelteKit and the new `bundleStrategy: 'inline'` option

Day 22 — you can now use the `bundleStrategy: 'inline'` option to build an entire SvelteKit app — code, styles, fonts, images, audio, and so on — into a single `.html` file that you can share on a floppy disk

🎁 docs svelte.dev/docs/kit/con...
🎁 demo svelte-snek.vercel.app (needs keyboard for now!)

Configuration • Docs • Svelte Configuration • Svelte documentation

Day 21 — hash-based routing for SvelteKit apps, for when you don't need (or can't run) a server. You can't use any server-side logic (including SSR), but other than, it's just like any other SvelteKit app

🎁 docs svelte.dev/docs/kit/con...
🎁 demo hash-based-routing.vercel.app

Day 20 — Vim mode! You can enable it in the playground and tutorial and it will remember your preference between visits. Don't worry, you can always quit by turning it off again (or closing the tab)

🎁 svelte.dev/playground

Svelte Summit Spring 2025: Barcelona & online The next in-person Svelte Summit will happen on May 8 and 9 in Barcelona, Spain! Get your tickets and submit your proposals now!

Reminder: There are less than two weeks left to get a 20% discount on tickets for the next in-person Svelte Summit. Use the code sveltmas2024 at checkout or email us for group tickets. More details on the website. www.sveltesummit.com

👀

a screenshot showing the new `output.bundleStrategy` option in SvelteKit. On the left, the updated svelte.config.js; on the right, a look at the resulting HTML

Day 19 — single-file bundles for SvelteKit. By default, your apps use code-splitting to ensure that you only load the code for the current page. But sometimes you need a single bundle for the whole app, and you can now do that with the new `bundleStrategy` option

🎁 docs svelte.dev/docs/kit/con...

Day 18 — we've upgraded the playground so you can better understand how the compiler transforms your code. We plan to use this tool ourselves to improve the sourcemaps that Svelte generates

🎁 svelte.dev/playground

Day 17 — until today, intellisense would often fail when you were in the middle of writing components, because Svelte's parser crashed on syntax errors.

We just fixed that. Install svelte@latest, make sure your extensions are up to date, and feel the wind in your hair as you write your components

note: you can migrate automatically using the following command

npx sv migrate app-state

$app/state • Docs • Svelte $app/state • Svelte documentation

Day 16 — `$app/state`, a modern Svelte 5 state-based replacement for SvelteKit's `$app/stores` module. No more clunky `$` prefix when reading values, just fine-grained state that works everywhere, even outside component files!

🎁 docs svelte.dev/docs/kit/$ap...
🎁 tutorial svelte.dev/tutorial/kit...