eCTD is the electronic version of CTD (the Common Technical Document). CTD is a harmonised format for submission of detailed information on medicines to regulatory authorities for the purposes of obtaining approval to market a product.

The specification for the eCTD was developed by ICH (the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use). ICH brings together the regulatory authorities of Europe, Japan and the United States and experts from the pharmaceutical industry to discuss scientific and technical aspects of medicines registration, with the aim of achieving a greater degree of harmonisation between these three regions. The work of ICH is organised in a series of discrete topics.

The specification for eCTD was developed under ICH Topic M2 in parallel with Topic M4 (CTD), and was finalised in November 2003. There is no difference between CTD and eCTD in terms of scientific, technical and clinical content. However, there are regional differences in implementation of eCTD between ICH regions.

An eCTD is simply a standard electronic format for sending data from the applicant to the regulatory authority. In theory, eCTD is vendor and system independent, in terms of both creation and use.  In practice, there have been some reports of issues with interoperability between different eCTD tools, because vendors have not always interpreted the eCTD specifications in the same way.