The reCAPTCHA security image is made up of two parts:
  • A piece of text that is secure and bot-proof
  • An image of text which does not affect security.

When users respond to reCAPTCHA prompts, they only need to get the bot-proof part correct. 

The additional piece is an image from a digitization project. It may be part of a book or a street sign. Based on input from multiple users, reCAPTCHA helps to translate digitized books and identify streets. Because this piece is only used to benefit the digitization project, the user's input does not need to match the prompt exactly to pass the security check.