If you're building with SvelteKit and want to improve how your site gets discovered by search engines, setting up a sitemap.xml is a good place to start. This guide walks through how to generate a dynamic sitemap in SvelteKit using +server.ts, and how to optionally include lastmod timestamps for better indexing.

Why Use a Sitemap?

A sitemap is a structured list of your site’s URLs. Search engines use it to understand what content exists on your site and when it was last updated. It becomes particularly important if:

• Your site has dynamic content (e.g., blog posts or product pages)

• Not all pages are easily discoverable via internal links

• You want faster indexing after publishing or updating content

Step 1: Create a Dynamic Sitemap Route in SvelteKit

Create a file at:

src/routes/sitemap.xml/+server.ts

paste the following code:

const baseUrl = 'https://example.com';

export async function GET() {
	const pages = [
		{ url: '/', lastmod: '2024-12-15' },
		{ url: '/about', lastmod: '2024-12-10' }
	];

	const sitemap = `<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
${pages
	.map(
		(page) => `
	<url>
		<loc>${new URL(page.url, baseUrl)}</loc>
		<lastmod>${page.lastmod}</lastmod>
	</url>`
	)
	.join('')}
</urlset>`;

	return new Response(sitemap, {
		headers: {
			'Content-Type': 'application/xml'
		}
	});
}

When you visit /sitemap.xml, you should see a valid XML response with your listed pages.

How the Code Works

• baseUrl is your site's root URL. Update this to your production domain.

• The pages array lists the routes you want indexed. You can hardcode static routes or dynamically fetch content.

• Each item is converted into a valid <url> block inside the XML using .map().

• The Content-Type header ensures the browser and crawlers interpret it as XML.

Adding Dynamic Routes

If you have dynamic content like blog posts or documentation pages, you can fetch those slugs and generate URLs programmatically. For example:

const posts = await getAllBlogSlugs();

const pages = posts.map((slug) => ({
	url: `/blog/${slug}`,
	lastmod: '2024-12-20' // optionally use actual update timestamps
}));

Combine these with your static pages to build a full sitemap.

Should You Include the lastmod Tag?

The lastmod field indicates when a page was last modified. It's optional but can help search engines prioritize recent updates.

Use lastmod if:

• Your content is regularly updated

• You want faster reindexing of updated pages

• Your SEO strategy benefits from content freshness

It’s less critical if:

• Your content is mostly static

• Your site is small and easily crawlable

• You don’t track publish/update dates

If omitted, your sitemap remains valid, but may be crawled less efficiently.

Validation and Submission

Once implemented, test your sitemap:

• Visit /sitemap.xml and inspect the output

• Validate it using tools like Google’s sitemap validator

To notify search engines, add this line to your robots.txt file:

Sitemap: https://example.com/sitemap.xml

You can also submit it via Google Search Console for faster indexing.

Conclusion

A dynamic sitemap helps search engines crawl and index your SvelteKit site more effectively. Whether you're working with a handful of static pages or hundreds of dynamic routes, implementing a sitemap with +server.ts is a lightweight, scalable approach. By optionally including lastmod data, you give crawlers even more context for what’s new and relevant.

If your site evolves over time, your sitemap should evolve with it—and this setup makes that straightforward.