SeleniumHQ/selenium · error · Error

Http method must be a string. Received: '${method})'

Error message

Http method must be a string. Received: '${method})'

What it means

Thrown by `ContinueRequestParameters.method()` when the argument is not a string (`typeof method !== 'string'`). The method stores the value directly into the BiDi command map. The error string carries a cosmetic typo: an extra `)` (`'${method})'`).

Source

Thrown at javascript/selenium-webdriver/bidi/continueRequestParameters.js:95

        throw new Error(`Header value must be an instance of Header. Received:'${header}'`)
      }
      headerList.push(Object.fromEntries(header.asMap()))
    })

    this.#map.set('headers', headerList)
    return this
  }

  /**
   * Sets the HTTP method for the request.
   *
   * @param {string} method - The HTTP method to be set.
   * @returns {ContinueRequestParameters} - The updated `continueRequestParameters` object.
   * @throws {Error} - If the method parameter is not a string.
   */
  method(method) {
    if (typeof method !== 'string') {
      throw new Error(`Http method must be a string. Received: '${method})'`)
    }
    this.#map.set('method', method)
    return this
  }

  /**
   * Sets the URL for the request.
   *
   * @param {string} url - The URL to set for the request.
   * @returns {ContinueRequestParameters} - The current instance of the ContinueRequestParameters for chaining.
   * @throws {Error} - If the url parameter is not a string.
   */
  url(url) {
    if (typeof url !== 'string') {
      throw new Error(`Url must be a string. Received:'${url}'`)
    }

    this.#map.set('url', url)

View on GitHub (pinned to aa36b38e69)

Solutions

1. Pass a plain string such as 'GET', 'POST', 'PUT', 'DELETE'
2. Ensure the variable is defined and is a string before calling

Example fix

// before
params.method(req.methodNumber)
// after
params.method('POST')

if (typeof method === 'string') params.method(method)

const isHttpMethod = (m) => typeof m === 'string'

When it happens

Trigger: Calling `params.method(undefined)`, `params.method(200)`, or passing a numeric/enum object instead of a string verb.

Common situations: Passing a method from a typed enum that resolves to a non-string; forgetting to set the method so it is undefined; confusing an HTTP status number with the method.

Related errors

• Reason phrase must be a string. Received: '${reasonPhrase})'
• Value must be an instance of BytesValue. Received: '${value}
• Url must be a string. Received:'${url}'
• Username must be a string. Received:'${username}'
• Password must be a string. Received:'${password}'

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/aaa2eacb0ed30838. Report an issue: GitHub.