svelte/documentation/docs/07-misc/05-browser-support.md

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Browser support

The table below shows the minimum browser versions Svelte's runtime and compiled output are expected to work in.

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These numbers describe what Svelte's output requires in order to run — they're derived from the APIs the code uses, not from a list of browsers the team commits to testing.

What is covered

• Svelte's runtime. Everything you import from svelte or its subpackages, in the form your bundler ships to the browser.
• Compiler output. The JavaScript the Svelte compiler emits from your .svelte files, including the DOM operations, bindings and transitions used in your components.

What is not covered

• Your own code inside <script> blocks or .svelte.js files. If you use newer browser APIs the table will not reflect them — configure your own browserslist and polyfills accordingly.
• SvelteKit, adapters and build tooling. See the SvelteKit docs for the browser support story there.
• Internet Explorer 11. Svelte's runtime relies on Proxy, which cannot be polyfilled. IE11 is not supported and there is no path to making it work.

Per-feature browser requirements

Some Svelte features rely on browser APIs that exceed the floor above. The runtime still loads on older browsers — modern bundlers tree-shake the affected code when the feature is unused — but if you use one of these features, you need the higher minimum version listed here.

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How this page stays accurate

The minimum versions can only move forward in a minor or major release, and any change is recorded in the changelog. Every Svelte feature — bindings, runes, directives, and module exports — is checked against the web-features Baseline dataset on every pull request, and the build fails if a change requires newer browsers than the page reflects.