We modified the traditional (verbal) digit span task for administration via computer and the Internet. This online version collects data on the floor and ceiling of a subject’s span capacity, rather than generating a rough estimate of capacity based on a 50% success rate, as the traditional version does. We compared the two versions within adult subjects in two cohorts: college-age normal readers and college-age reading-disabled readers. To explore the reliability of the online version as a research tool, we employed the Bland-Altman approach to examine agreement between instruments. The online version yielded spans similar to those yielded by the traditional version, tending toward smaller values at the high end and larger values at the low end of span sizes, in the typical readers. It differentiated between the better and poorer readers reliably, and to the same extent as does the verbal version. The online version of the digit span task is comparable to the traditional version in assessing verbal span capacity; the code with which to implement the task is available at www.psychonomic.org/archive.