See for examples of seal script compared to modern Chinese script.
Most people today cannot read the seal script, so it is generally not used outside the fields of seals and calligraphy.
Large Seal Scripts
There are two uses of the word seal script, the , and the lesser or ; the latter is also called simply ''seal script''. The Large Seal script was originally a later, vague Han dynasty reference to writing of the Qin system similar to but earlier than Small Seal. It has also been used to refer to Western Zhou forms or even oracle bones as well. Since the term is an imprecise one, not clearly referring to any specific historical script and not used with any consensus in meaning, modern scholars tend to avoid it, and when referring to ''seal'' script, generally mean the seal script of the Qin system, that is, the lineage which evolved in the state of Qin during the Spring and Autumn to Warring States periods and which was standardized under the First Emperor.
Evolution of Seal Script
Unified Small seal script
The script of the Qin system had evolved organically from the Zhou script starting in the Spring and Autumn period. Beginning around the Warring States period, it became vertically elongated with a regular appearance. This was the period of maturation of Small Seal script, also called simply ''seal script''. It was systematized by Li Si 李斯 during the reign of the First Emperor of China Qin Shi Huang through elimination of most variant structures, and was imposed as the nationwide standard , but small seal script was clearly not ''invented'' at that time. Through Chinese commentaries, it is known that Li Si compiled ''Cangjie'' 倉頡篇, a non-extant work of character recognition listing some 3,300 Chinese characters in small seal script. Their form is characterised by being less rectangular and more squarish.
In the popular history of Chinese characters, the Small Seal script is traditionally considered to be the ancestor of the clerical script 隷書, which in turn gave rise to all of the other scripts in use today. However, recent archaeological discoveries and scholarship have led some scholars to conclude that the direct ancestor of clerical script was proto-clerical script, which in turn evolved out of the little-known ''vulgar'' or ''popular'' writing of the late Warring States to Qin period .
The first known character dictionary was the 3rd century BC ''Erya'' 爾雅, collated and bibliographed by Liu Xiang 劉向 and his son Liu Xin 劉歆, lost the pre-Han script during the course of textual transmission. Not long after however, the ''Shuowen Jiezi'' 說文解字 was written preserving the canonical small seal script of late-Qin. The latter shows 9,353 pre-Han scripts, consisting mostly of the late Qin small seal script characters and a small number of Six Warring States variant scripts, listed under 540 , the lifework of Xu Shen 許愼, during the Han Dynasty.