vercel/next.js · error · Error

You cannot use different slug names for the same dynamic pat

Error message

You cannot use different slug names for the same dynamic path ('${previousSlug}' !== '${nextSlug}').

What it means

handleSlug throws when a dynamic segment level already has a slug name and another route at the same level uses a different one (e.g. pages/[post]/x and pages/[id]/x). Only one dynamic parameter name is allowed per level because the router stores a single param value for that position.

Source

Thrown at packages/next/src/shared/lib/router/utils/sorted-routes.ts:130

        )
      }

      if (segmentName.startsWith('.')) {
        throw new Error(
          `Segment names may not start with erroneous periods ('${segmentName}').`
        )
      }

      function handleSlug(previousSlug: string | null, nextSlug: string) {
        if (previousSlug !== null) {
          // If the specific segment already has a slug but the slug is not `something`
          // This prevents collisions like:
          // pages/[post]/index.js
          // pages/[id]/index.js
          // Because currently multiple dynamic params on the same segment level are not supported
          if (previousSlug !== nextSlug) {
            // TODO: This error seems to be confusing for users, needs an error link, the description can be based on above comment.
            throw new Error(
              `You cannot use different slug names for the same dynamic path ('${previousSlug}' !== '${nextSlug}').`
            )
          }
        }

        slugNames.forEach((slug) => {
          if (slug === nextSlug) {
            throw new Error(
              `You cannot have the same slug name "${nextSlug}" repeat within a single dynamic path`
            )
          }

          if (slug.replace(/\W/g, '') === nextSegment.replace(/\W/g, '')) {
            throw new Error(
              `You cannot have the slug names "${slug}" and "${nextSlug}" differ only by non-word symbols within a single dynamic path`
            )
          }
        })

View on GitHub (pinned to 0eb3775416)

Solutions

1. Use the same slug name for the same dynamic path across routes.

When it happens

Trigger: Two routes use different slug names for the same dynamic path.

Common situations: /blog/[id] and /blog/[postId] both exist; the slug names must match.

AI-assisted analysis of vercel/next.js@0eb3775416 (2026-08-19). Data as JSON: /api/errors/6f8257b1278b4b8f. Report an issue: GitHub.