What causes "Missing params for dynamic route ID ${id}" in sveltejs/kit?

Pass a params object matching the route's dynamic segments: resolve('/blog/[slug]', { slug: 'hello' })

sveltejs/kit · error · Error

Missing params for dynamic route ID ${id}

Error message

Missing params for dynamic route ID ${id}

What it means

The $app/paths resolve() function builds URLs from route IDs. When given a route ID containing dynamic segments (e.g. /blog/[slug]) as the first argument, it requires a params object to fill those segments; without one the generated URL would be invalid, so it throws.

Source

Thrown at packages/kit/src/runtime/app/paths/client.js:73

 *
 * // using a route ID plus parameters
 * const resolved = resolve('/blog/[slug]', {
 * 	slug: 'hello-world'
 * });
 * ```
 * @since 2.26
 *
 * @template {RouteIdWithSearchOrHash | PathnameWithSearchOrHash} T
 * @param {ResolveArgs<T>} args
 * @returns {ResolvedPathname}
 */
export function resolve(...args) {
	const [id, params] = /** @type {[string, Record<string, string>?]} */ (args);

	if (id[0] === '/') {
		// route ID
		if (id.includes('[') && !params) {
			throw new Error(`Missing params for dynamic route ID ${id}`);
		}

		return (
			/** @type {ResolvedPathname} */ (base + pathname_prefix + resolve_route(id, params ?? {}))
		);
	}

	return /** @type {ResolvedPathname} */ (base + pathname_prefix + '/' + id);
}

/**
 * Match a path or URL to a route ID and extracts any parameters.
 *
 * @example
 * ```js
 * import { match } from '$app/paths';
 *
 * const route = await match('blog/hello-world');

View on GitHub (pinned to 03f1687fe6)

Solutions

Pass a params object matching the route's dynamic segments: resolve('/blog/[slug]', { slug: 'hello' })
For static route IDs, omit brackets or simply don't pass params (they default to {})
Check that the ID is a real route from generated route types; use type checking so RouteId/RouteParams catch mismatches at compile time

Example fix

// before
const url = resolve('/blog/[id]');
// after
const url = resolve('/blog/[id]', { id: '42' });

Defensive patterns

Strategy: validation

Validate before calling

import { resolve } from '$app/paths';
/** @type {Record<string, string>} */
const params = { slug: 'hello' };
if (id.includes('[') && (!params || Object.keys(params).length === 0)) {
  throw new Error(`resolve('${id}') requires params`);
}
const url = resolve(id, params);

Type guard

/** @template {string} T */
const isDynamicRouteId = (id) => typeof id === 'string' && id.startsWith('/') && id.includes('[');

Try / catch

try {
  const url = resolve(routeId, params);
} catch (e) {
  if (e.message.startsWith('Missing params for dynamic route ID')) {
    console.error(`Provide params for ${routeId}`);
  } else throw e;
}

Prevention

Always pass a params object for route IDs containing [..] segments
Use TypeScript with generated $app/types RouteParams so missing params fail at compile time
Prefer named route helpers or href generation from route types
Validate params are complete before calling resolve in shared utilities

When it happens

Trigger: resolve('/blog/[slug]') — a route ID containing '[' passed with no second params argument — from client code using $app/paths.

Common situations: Forgetting to pass params for dynamic routes while using route-ID based resolution (SvelteKit 2.12+ route IDs), passing params only for some call sites, or mistakenly treating a static route pattern with brackets as a path prefix.

Related errors

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/a16b5e03c64eecc8. Report an issue: GitHub.