# What's new in Svelte: March 2021

DevFeed: [What's new in Svelte: March 2021](<https://devfeed.tech/articles/what-s-new-in-svelte-march-2021-3098.md>)

Original publisher: [Read original article](<https://svelte.dev/blog/whats-new-in-svelte-march-2021>)

Author: Dani Sandoval

Published: 2021-03-01T00:00:00Z

Content type: news

Language: en

Sources: [Svelte blog](<https://devfeed.tech/sources/svelte-blog.md>)

Topics: [Svelte](<https://devfeed.tech/topics/svelte.md>), [releases](<https://devfeed.tech/topics/releases.md>), [Server-side rendering](<https://devfeed.tech/topics/server-side-rendering.md>), [TypeScript](<https://devfeed.tech/topics/typescript.md>), [Web Components](<https://devfeed.tech/topics/web-components.md>), [ESLint](<https://devfeed.tech/topics/eslint.md>), [Prettier](<https://devfeed.tech/topics/prettier.md>), [Visual Studio Code](<https://devfeed.tech/topics/visual-studio-code.md>), [CSS](<https://devfeed.tech/topics/css.md>)

Tags: [components](<https://devfeed.tech/tags/components.md>), [eslint](<https://devfeed.tech/tags/eslint.md>), [releases](<https://devfeed.tech/tags/releases.md>), [ssr](<https://devfeed.tech/tags/ssr.md>), [svelte](<https://devfeed.tech/tags/svelte.md>), [tools](<https://devfeed.tech/tags/tools.md>), [typescript](<https://devfeed.tech/tags/typescript.md>), [vscode](<https://devfeed.tech/tags/vscode.md>)

## AI overview

A March 2021 update covering releases across the Svelte ecosystem, including Svelte core, language tools, plugins, preprocessors, and Sapper. It highlights improvements to SSR stores, actions, compiler namespaces and CSS scoping, TypeScript definitions, editor tooling, parsing, and related ecosystem packages.

## Source excerpt

Lots to cover this month with releases from across the Svelte ecosystem. Most importantly, Svelte Summit Spring 2021 has an Open Call for Speakers. The deadline is March 14 so if you have an idea for a talk, submit it now! Let's dive into the news 🐬 What's new in sveltejs/svelte SSR store handling has been reworked to subscribe and unsubscribe as in DOM mode. SSR stores should work much more consistently now (3.31.2, see custom stores and Server-side component API ) Multiple instances of the same action are now allowed on an element (3.32.0, example) The new foreign namespace should make it easier for alternative compile targets (like Svelte Native and SvelteGUI) by disabling certain HTML5-specific behaviour and checks (3.32.0, more info) Support for inline comment sourcemaps in code from preprocessors (3.32.0) Destructured defaults are now allowed to refer to other variables (3.33.0, example) Custom elements will now call onMount functions when connecting and clean up when disconnecting (3.33.0, checkout this PR for an interesting conversation on how folks are using Svelte with Web Components) A cssHash option has been added to the compiler options to control the classname used for CSS scoping (3.34.0, docs) Continued improvement to TypeScript definitions For a complete list of changes, including bug fixes and links to PRs, check out the CHANGELOG New from sveltejs/language-tools For language server clients that don't support didChangeWatchedFiles, a fallback file watcher will be used instead New highlighting rules for store accessors and element directives (like bind: and class:) HTML tags can now be renamed together Mustache tags parsing is now more robust and will provide better intellisense in more situations Haven't tried the language-tools yet? Check out Svelte Extension for VSCode or find a plugin for your favorite IDE! Other changes from sveltejs/* eslint-plugin-svelte3 now supports TypeScript as of 3.1.0 prettier-plugin-svelte released a number of minor ve