SeleniumHQ/selenium · error · Error

Pattern must be an instance of UrlPattern. Received: '${patt

Error message

Pattern must be an instance of UrlPattern. Received: '${pattern})'

What it means

AddInterceptParameters.urlPattern() (WebDriver BiDi network.addIntercept) validates that the single pattern argument is an instance of the UrlPattern class from ./urlPattern. UrlPattern is the only structured-pattern type in BiDi network interception (alongside plain string patterns handled by urlStringPattern). Passing a plain object, a string, a Map, or an instance from a different module realm fails the instanceof check. The error message interpolates the received value — note the literal has a stray ')' producing `Received: '<value>)'`, a minor message bug.

Source

Thrown at javascript/selenium-webdriver/bidi/addInterceptParameters.js:41

  constructor(phases) {
    if (phases instanceof Array) {
      phases.forEach((phase) => this.#phases.push(phase))
    } else {
      this.#phases.push(phases)
    }
  }

  /**
   * Adds a URL pattern to intercept.
   *
   * @param {UrlPattern} pattern - The URL pattern to add.
   * @returns {AddInterceptParameters} - Returns the current instance of the class AddInterceptParameters for chaining.
   * @throws {Error} - Throws an error if the pattern is not an instance of UrlPattern.
   */
  urlPattern(pattern) {
    if (!(pattern instanceof UrlPattern)) {
      throw new Error(`Pattern must be an instance of UrlPattern. Received: '${pattern})'`)
    }
    this.#urlPatterns.push(Object.fromEntries(pattern.asMap()))
    return this
  }

  /**
   * Adds array of URL patterns to intercept.
   *
   * @param {UrlPattern[]} patterns - An array of UrlPattern instances representing the URL patterns to intercept.
   * @returns {AddInterceptParameters} - Returns the instance of AddInterceptParameters for chaining.
   * @throws {Error} - Throws an error if the pattern is not an instance of UrlPattern.
   */
  urlPatterns(patterns) {
    patterns.forEach((pattern) => {
      if (!(pattern instanceof UrlPattern)) {
        throw new Error(`Pattern must be an instance of UrlPattern. Received:'${pattern}'`)
      }
      this.#urlPatterns.push(Object.fromEntries(pattern.asMap()))

View on GitHub (pinned to aa36b38e69)

Solutions

1. Construct a UrlPattern via new UrlPattern() and chain .protocol()/.hostname()/.pathname() etc. before passing it to urlPattern().
2. If you only have a URL string, use urlStringPattern(url) or urlStringPatterns([urls]) instead.
3. Ensure a single copy of selenium-webdriver is installed (dedupe node_modules) so instanceof works.
4. Do not pass plain objects or Map instances; only UrlPattern instances are accepted.

Example fix

// before
params.urlPattern({ protocol: 'https', hostname: 'example.com' })

// after
const { UrlPattern } = require('selenium-webdriver/bidi/urlPattern')
const pattern = new UrlPattern().protocol('https').hostname('example.com')
params.urlPattern(pattern)

if (!(pattern instanceof UrlPattern)) {
  throw new TypeError('urlPattern expects a UrlPattern instance')
}

function isUrlPattern(p) {
  return p instanceof UrlPattern
}

When it happens

Trigger: Calling addInterceptParameters.urlPattern({ protocol: 'https' }) with a plain object instead of a UrlPattern instance. Passing a string URL (should use urlStringPattern instead). Passing a UrlPattern constructed in a different Node module instance/realm where instanceof fails. Passing null/undefined.

Common situations: Confusing urlPattern (structured) with urlStringPattern (plain string). Copying example code that builds a raw object. Multiple copies of the selenium-webdriver package installed, causing instanceof to fail across realms. Importing UrlPattern from the wrong path.

Related errors

• Pattern must be an instance of UrlPattern. Received:'${patte
• Pattern must be an instance of String. Received:'${pattern}'
• Params must be an instance of AddInterceptParameters. Receiv
• Params must be an instance of ContinueRequestParameters. Rec
• Params must be an instance of ContinueResponseParameters. Re

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/89bde9803f532e4f. Report an issue: GitHub.