Big employers such as AT&T Inc. and Google Inc. are helping to design and fund the latest round of low-cost online courses, a development that providers say will open the door for students to earn inexpensive credentials with real value in the job market.

New niche certifications being offered by providers of massive open online courses, or MOOCs, are aimed at satisfying employers' specific needs. Available at a fraction of the cost of a four-year degree, they represent the latest crack in the monopoly traditional universities...