SeleniumHQ/selenium · error · Error::NoSuchTargetError

Target type '#{target_type}' not found

Error message

Target type '#{target_type}' not found

What it means

Raised as Error::NoSuchTargetError during DevTools session startup (start_session) when none of the targets returned by Target.getTargets match the requested target_type. The DevTools endpoint enumerates available browser targets and attaches to the first whose 'type' equals the requested value; if none matches, there is no target to attach to.

Source

Thrown at rb/lib/selenium/webdriver/devtools.rb:87

          define_method(method) do
            Object.const_get(desired_class).new(self)
          end
        end

        send(method)
      end

      def respond_to_missing?(method, *_args)
        desired_class = "Selenium::DevTools::V#{Selenium::DevTools.version}::#{method.capitalize}"
        Object.const_defined?(desired_class)
      end

      private

      def start_session(target_type:)
        targets = target.get_targets.dig('result', 'targetInfos')
        found_target = targets.find { |target| target['type'] == target_type }
        raise Error::NoSuchTargetError, "Target type '#{target_type}' not found" unless found_target

        session = target.attach_to_target(target_id: found_target['targetId'], flatten: true)
        @session_id = session.dig('result', 'sessionId')
      end

      def error_message(error)
        [error['code'], error['message'], error['data']].join(': ')
      end
    end # DevTools
  end # WebDriver
end # Selenium

View on GitHub (pinned to aa36b38e69)

Solutions

1. Ensure a page target exists before connecting DevTools (open/navigate a tab first).
2. Pass a target_type that matches an actual returned target type (commonly 'page'); inspect available targets via the CDP Target.getTargets to confirm.
3. If attaching to a non-page target, verify the browser version supports that target type and that such a target is currently live.

Example fix

// before
devtools = driver.devtools  # fails if no 'page' target present

// after
driver.get('https://example.com')  # ensure a page target exists first
devtools = driver.devtools

# Ensure a page target exists before connecting DevTools
driver.get(base_url) unless driver.window_handles.any?
begin
  devtools = driver.devtools
rescue Selenium::WebDriver::Error::NoSuchTargetError => e
  raise "No DevTools target available: #{e.message}"
end

begin
  devtools = driver.devtools
rescue Selenium::WebDriver::Error::NoSuchTargetError => e
  WebDriver.logger.warn("DevTools attach failed: #{e.message}")
  retry_after_opening_page
end

When it happens

Trigger: Initializing driver.devtools (or DevTools.new) with a target_type that does not exist among current targets, e.g. 'page' when no tab/page target is open, or a misspelled/unsupported type like 'tab' or 'iframe'.

Common situations: Connecting DevTools to a browser whose only targets are background/service-worker types; calling devtools before navigating to any page; passing a non-standard target_type string; version mismatches where the browser exposes different target categories.

Related errors

• {fn_name}() must be called in a session context.
• CDP devtools module not loaded. Call import_devtools() first
• CDP version not found in capabilities
• Unable to find url to connect to from capabilities
• CDP module not loaded

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/894ae944d83a7c23. Report an issue: GitHub.