Fix: Invalid Value Returned From getStaticPaths() in Astro

Astro reports “Invalid value returned by a route from getStaticPaths()” when one of the objects you return has a params value that isn’t an object. Each route must look like { params: { slug: 'my-post' } }. Returning { params: 'my-post' }, an array, or undefined triggers this error. The full message says: “Invalid params value returned by a route from getStaticPaths(). Expected an object,” followed by what it received.

Key Takeaways

• params must be an object whose keys match the brackets in the file name.
• Values must be strings (or undefined for an optional rest param).
• Pass extra data through props, not params.
• When mapping data, check you’re not returning the raw item by accident.

What a valid return value looks like

// src/pages/blog/[slug].astro
export async function getStaticPaths() {
  return [
    { params: { slug: 'first-post' }, props: { title: 'First post' } },
    { params: { slug: 'second-post' }, props: { title: 'Second post' } },
  ];
}

For several parameters, as in src/pages/[lang]/[slug].astro:

return [{ params: { lang: 'en', slug: 'pricing' } }];

For a rest parameter, as in src/pages/docs/[...path].astro:

return [
  { params: { path: 'getting-started/install' } },
  { params: { path: undefined } }, // serves /docs/
];

Typical mistakes

Returning a string as params

// Wrong
return posts.map((post) => ({ params: post.id }));

// Right
return posts.map((post) => ({ params: { slug: post.id } }));

Returning the item instead of a route

// Wrong: each element is a post object, not { params }
return posts;

Map to { params, props } first.

Nesting params in props by mistake

// Wrong
return posts.map((post) => ({ props: { params: { slug: post.id } } }));

Related errors

If the object exists but has no keys, Astro shows Missing params property on getStaticPaths() route. If params are valid but a URL still doesn’t resolve, see No static path found.

Type it to catch this earlier

Use the GetStaticPaths type so your editor flags bad shapes before you build:

import type { GetStaticPaths } from 'astro';

export const getStaticPaths = (async () => {
  const posts = await getCollection('blog');
  return posts.map((post) => ({ params: { slug: post.id }, props: { post } }));
}) satisfies GetStaticPaths;

Run npx astro check to type-check every page. The Astro routing guide explains dynamic routes fully, and the routing reference documents every field.

FAQ

Can params values be numbers in Astro?

No. They must be strings. Convert with String(value).

Where should I put data the page needs?

In props. The page reads it from Astro.props, which avoids a second lookup.