With Capybara, how do I switch to the new window for links with "_blank" targets?

Capybara >= 2.3 includes the new window management API. It can be used like:

new_window = window_opened_by { click_link 'Something' }
within_window new_window do
  # code
end

This solution only works for the Selenium driver

All open windows are stores in Selenium's

response.driver.browser.window_handles

Which seems to be an array. The last item is always the window that was most recently opened, meaning you can do the following to switch to it.

Within a block:

new_window=page.driver.browser.window_handles.last 
page.within_window new_window do
  #code
end

Simply refocus for current session:

session.driver.browser.switch_to.window(page.driver.browser.window_handles.last)

Referenced on the capybara issues page: https://github.com/jnicklas/capybara/issues/173

More details on Selenium's window switching capabilities: http://qastuffs.blogspot.com/2010/10/testing-pop-up-windows-using-selenium.html

This is now working with Poltergeist. Although window_handles is still not implemented (you need a window name, i.e. via a JavaScript popup):

within_window 'other_window' do
  current_url.should match /example.com/
end

Edit: Per comment below, Poltergeist now implements window_handles since version 1.4.0.

Capybara provides some methods to ease finding and switching windows:

facebook_window = window_opened_by do
  click_button 'Like'
end
within_window facebook_window do
  find('#login_email').set('[email protected]')
  find('#login_password').set('qwerty')
  click_button 'Submit'
end

More details here: Capybara documentation

I know this is old post, but for what its worth in capybara 2.4.4

within_window(switch_to_window(windows.last)) do 
    # in my case assert redirected url from a prior click action
    expect(current_url).to eq(redirect['url'])
end