SeleniumHQ/selenium · error · Error

Value must be an instance of BytesValue. Received:'${value}'

Error message

Value must be an instance of BytesValue. Received:'${value}'

What it means

Thrown by `CookieFilter.value()` when the argument is not a `BytesValue` instance. The method calls `value.asMap()` to serialize the cookie value into the getCookies filter, so it requires a real `BytesValue` carrying a type and value — a raw string is rejected.

Source

Thrown at javascript/selenium-webdriver/bidi/cookieFilter.js:47

   *
   * @param {string} name - The name of the cookie.
   * @returns {CookieFilter} - The updated CookieFilter instance for chaining.
   */
  name(name) {
    this.#map.set('name', name)
    return this
  }

  /**
   * Sets the value of the cookie.
   *
   * @param {BytesValue} value - The value to be set. Must be an instance of BytesValue.
   * @returns {CookieFilter} - The updated CookieFilter instance for chaining.
   * @throws {Error} - If the value is not an instance of BytesValue.
   */
  value(value) {
    if (!(value instanceof BytesValue)) {
      throw new Error(`Value must be an instance of BytesValue. Received:'${value}'`)
    }
    this.#map.set('value', Object.fromEntries(value.asMap()))
    return this
  }

  /**
   * Sets the domain for the cookie.
   *
   * @param {string} domain - The domain to set.
   * @returns {CookieFilter} - The updated CookieFilter instance for chaining.
   */
  domain(domain) {
    this.#map.set('domain', domain)
    return this
  }

  /**
   * Sets the url path for the cookie to be fetched.

View on GitHub (pinned to aa36b38e69)

Solutions

1. Wrap the value in `new BytesValue(BytesValue.Type.STRING, value)`
2. Import `{ BytesValue }` from `selenium-webdriver/bidi/networkTypes`
3. value() is optional in CookieFilter — omit it if you do not have a BytesValue

Example fix

// before
filter.value('sessionid')
// after
const { BytesValue } = require('selenium-webdriver/bidi/networkTypes')
filter.value(new BytesValue(BytesValue.Type.STRING, 'sessionid'))

const { BytesValue } = require('selenium-webdriver/bidi/networkTypes')
if (value instanceof BytesValue) filter.value(value)

const { BytesValue } = require('selenium-webdriver/bidi/networkTypes')
const isBytesValue = (v) => v instanceof BytesValue

When it happens

Trigger: Calling `filter.value('sessionid')` with a raw string; passing `{type:'string', value:'x'}`; reusing a Cookie's value getter without confirming it is a BytesValue.

Common situations: Developers assume a plain string cookie value works; building a filter from deserialized cookie data.

Related errors

• Value must be an instance of BytesValue. Received: '${value}
• CookieHeader must be an instance of Header. Received:'${head
• CookieHeader must be an instance of Header. Received:'${head
• ClipRectangle must be an instance of ClipRectangle. Received
• Header value must be an instance of Header. Received:'${head

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/f51bfd8112bee13d. Report an issue: GitHub.