Script detection service techniques are described. In an implementation, values representing individual text characters in a string of one or more text characters are identified to determine which human writing system is associated with the individual text characters. The values are compared to a table that associates subsets of values with individual human writing systems. The values are determined to be within a particular subset of values in the table that correspond to a particular human writing system. A particular human writing system is designated as associated with the string based on the values associated with the individual text characters in the string being within the particular subset of values that corresponds with the particular human writing system.