  We introduce $\textit{scadnano}$ (https://scadnano.org) (short for
"scriptable cadnano"), a computational tool for designing synthetic DNA
structures. Its design is based heavily on cadnano, the most widely-used
software for designing DNA origami, with three main differences:
  1. scadnano runs entirely in the browser, with $\textit{no software
installation}$ required.
  2. scadnano designs, while they can be edited manually, can also be created
and edited by a $\textit{well-documented Python scripting library}$, to help
automate tedious tasks.
  3. The scadnano file format is $\textit{easily human-readable}$. This goal is
closely aligned with the scripting library, intended to be helpful when
debugging scripts or interfacing with other software. The format is also
somewhat more expressive than that of cadnano, able to describe a broader range
of DNA structures than just DNA origami.
