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noSyncScripts

src/content/docs/linter/rules/no-sync-scripts.mdx

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import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="HTML" icon="seti:html"> :::caution This rule is part of the [nursery](/linter/#nursery) group. This means that it is experimental and the behavior can change at any time. ::: ## Summary - Rule available since: `v2.3.6` - Diagnostic Category: [`lint/nursery/noSyncScripts`](/reference/diagnostics#diagnostic-category) - This rule doesn't have a fix. - The default severity of this rule is [**information**](/reference/diagnostics#information). - Sources: - Same as [`@next/next/no-sync-scripts`](https://nextjs.org/docs/messages/no-sync-scripts)

How to configure

json
{
	"linter": {
		"rules": {
			"nursery": {
				"noSyncScripts": "error"
			}
		}
	}
}

Description

Prevent the usage of synchronous scripts.

A synchronous script can impact your webpage performance, read more on how to Efficiently load third-party JavaScript.

Examples

Invalid

html
<script src=""></script>
<pre class="language-text"><code class="language-text">code-block.html:1:1 <a href="https://biomejs.dev/linter/rules/no-sync-scripts">lint/nursery/noSyncScripts</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Unexpected synchronous script.</span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>&lt;script src=&quot;&quot;&gt;&lt;/script&gt; <strong> │ </strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Synchronous scripts can impact your webpage performance. Add the &quot;async&quot; or &quot;defer&quot; attribute.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit </span><span style="color: lightgreen;"><a href="https://biomejs.dev/linter/#nursery">https://biomejs.dev/linter/#nursery</a></span><span style="color: lightgreen;"> for more information.</span> </code></pre>

Valid

html
<script src="" async></script>
<script src="" defer></script>
<script src="" type="module"></script>
</TabItem> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> :::caution This rule is part of the [nursery](/linter/#nursery) group. This means that it is experimental and the behavior can change at any time. ::: ## Summary - Rule available since: `v2.3.6` - Diagnostic Category: [`lint/nursery/noSyncScripts`](/reference/diagnostics#diagnostic-category) - This rule doesn't have a fix. - The default severity of this rule is [**information**](/reference/diagnostics#information). - This rule belongs to the following domains: - [`react`](/linter/domains#react) - [`next`](/linter/domains#next) - Sources: - Same as [`@next/next/no-sync-scripts`](https://nextjs.org/docs/messages/no-sync-scripts)

How to configure

json
{
	"linter": {
		"rules": {
			"nursery": {
				"noSyncScripts": "error"
			}
		}
	}
}

Description

Prevent the usage of synchronous scripts.

A synchronous script can impact your webpage performance, read more on how to Efficiently load third-party JavaScript.

Examples

Invalid

jsx
const Invalid = () => <script src="https://third-party-script.js" />;
<pre class="language-text"><code class="language-text">code-block.jsx:1:23 <a href="https://biomejs.dev/linter/rules/no-sync-scripts">lint/nursery/noSyncScripts</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Unexpected synchronous script.</span> <strong><span style="color: Tomato;">&gt;</span></strong> <strong>1 │ </strong>const Invalid = () =&gt; &lt;script src=&quot;https://third-party-script.js&quot; /&gt;; <strong> │ </strong> <strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong><strong><span style="color: Tomato;">^</span></strong> <strong>2 │ </strong> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">Synchronous scripts can impact your webpage performance. Add the &quot;async&quot; or &quot;defer&quot; attribute. If using Next.js, consider the Script component instead.</span> <strong><span style="color: lightgreen;">ℹ</span></strong> <span style="color: lightgreen;">This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit </span><span style="color: lightgreen;"><a href="https://biomejs.dev/linter/#nursery">https://biomejs.dev/linter/#nursery</a></span><span style="color: lightgreen;"> for more information.</span> </code></pre>

Valid

jsx
const Valid = () => {
  return (
    <>
      <script src="https://third-party-script.js" async />
      <script src="https://third-party-script.js" defer />
      <script src="https://third-party-script.js" type="module" />
    </>
  );
}

Next.js

jsx
import Script from 'next/script'

const Valid = () => <Script src="https://third-party-script.js" />;
</TabItem> </Tabs>