vuejs/vue-router · warning

Duplicate param keys in route with path: "${path}"

Error message

Duplicate param keys in route with path: "${path}"

What it means

A route path declares the same param name more than once (e.g. '/:id/:id'), producing duplicate keys in the compiled regex. The param value would be overwritten ambiguously, so vue-router warns during path-to-regexp compilation in dev.

Source

Thrown at src/create-route-map.js:201

    } else if (process.env.NODE_ENV !== 'production' && !matchAs) {
      warn(
        false,
        `Duplicate named routes definition: ` +
          `{ name: "${name}", path: "${record.path}" }`
      )
    }
  }
}

function compileRouteRegex (
  path: string,
  pathToRegexpOptions: PathToRegexpOptions
): RouteRegExp {
  const regex = Regexp(path, [], pathToRegexpOptions)
  if (process.env.NODE_ENV !== 'production') {
    const keys: any = Object.create(null)
    regex.keys.forEach(key => {
      warn(
        !keys[key.name],
        `Duplicate param keys in route with path: "${path}"`
      )
      keys[key.name] = true
    })
  }
  return regex
}

function normalizePath (
  path: string,
  parent?: RouteRecord,
  strict?: boolean
): string {
  if (!strict) path = path.replace(/\/$/, '')
  if (path[0] === '/') return path
  if (parent == null) return path
  return cleanPath(`${parent.path}/${path}`)

View on GitHub (pinned to 680ccc68c5)

Solutions

1. Give each param a unique name: '/user/:userId/posts/:postId'
2. Inspect the generated path string if paths are built dynamically
3. Refactor so the same value is not captured twice (use one segment or a query param)
4. Test path matching after renaming params to update this.$route.params consumers

Example fix

// before
{ path: '/user/:id/posts/:id' }
// after
{ path: '/user/:userId/posts/:postId' }

function assertUniqueParams(path) {
  const names = (path.match(/:[^/?]+/g) || []).map(s => s.replace(/[^\w]/g, ''))
  const dupes = names.filter((n, i) => names.indexOf(n) !== i)
  if (dupes.length) throw new Error(`Duplicate params ${dupes} in path: ${path}`)
}

When it happens

Trigger: Paths like '/:id/:id', '/user/:id/posts/:id', or repeated optional params '/:a?/:a?' where key.name collides in regex.keys.

Common situations: Copy-paste of path segments; template-string path builders that interpolate the same param twice; renaming params in one place but not another.

Related errors

• props in "${route.path}" is a ${typeof config}, expecting an
• invalid redirect option: ${JSON.stringify(redirect)}
• Non-nested routes must include a leading slash character. Fi
• Route with path "${path}" contains unencoded characters, mak
• Named Route '${route.name}' has a default child route. When

AI-assisted analysis of vuejs/vue-router@680ccc68c5 (2026-09-02). Data as JSON: /api/errors/732a1ebc8881141d. Report an issue: GitHub.