The digit span test is a way of measuring the storage capacity of a person’s working memory: A testperson is visually or auditorily exposed to a sequence of digits one after the other. Right afterwards, the test subject has to recall the correct digits in the same order. Most people manage to recap around seven digits. I have written an online tool that lets the user determine their digit span test score. It is available at the website tools.timodenk.com/digit-span-test.
The tool’s most important features are auditive (English) and visual mode, adjustable time between two digits (1000 ms by default), and neither signup nor plugin requirements. You can try it in the iframe below.
More information about the working memory, a system temporarily holding information, can be found in the corresponding Wikipedia article. Back in 1956, George A. Miller has published an article — one of the most cited psychology papers — in which he examines the number 7, which is not only the digit span of most people. It can be found here: The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information