Ketcher is a web-based chemical structure editor.


Since Ketcher is written in pure Javascript, it incorporates high performance, good portability and light weight. You will not need any Java or Flash plugins to use it in your browser. Ketcher is completely free and open-source, while also available on a commercial basis.

You can easily integrate Ketcher into your web application. The process of integration is very simple and well-documented.


Ketcher is under active development. You can post us your comments and suggestions and get timely replies from the developers’ team.


Standalone mode

Ketcher supports the standalone mode in which no server support is required. In this mode, SMILES loading, automatic layout and automatic atom-atom mapping are not available.

Scalable Vector Graphics (SVG) for rendering

Ketcher uses Raphael as a backend, which means that SVG or VML (Vector Markup Language) is used for rendering, depending on the browser.

Automatic layout (clean up), AAM (atom-to-atom mapping) and (de)aromatization

Ketcher delegates these computationally intensive procedures to the Indigo toolkit on the server side.

Supported file formats

Ketcher can import and export Molfile/Rxnfile, as well as SMILES. Server is required to import a SMILES string, since layout is needed to obtain the coordinates.

Other features

Fast and convenient editing. We strive to make Ketcher as easy to use and as fast as the state-of-the-art desktop structure editing tools. See Editing Tips for details. Here are some highlights:

  • Lasso and Rectangle selection tools, plus a special Fragment selection tool to deal with connected components, rather than single atoms/bonds.

  • A variety of hotkeys.

  • Undo/Redo.

Stereochemistry. Ketcher provides complete stereochemistry support during the editing, loading, and saving of chemical structures.

Reactions. Full-featured reaction support including reacting centers, atom flags and AAM.

S-groups. All major S-group types are supported including generic, SRU polymers, multiple groups, superatoms and data S-groups.

R-groups. R-site and R-fragment assignment is supported, as well as attachment point specification and R-logic.

Supported browsers

The complete functionality of Ketcher has been tested on the following browsers:

  • Internet Explorer 6+

  • Firefox 3.5+

  • Safari 4+

  • Opera 9.6+

  • Chrome 2+

Third-party code

Ketcher makes use of Raphael and Prototype.

The current icon set was taken from Tango Desktop Project

Ketcher 2.0

Right now the new version of Ketcher is developed. It includes modern interface, good performance and lot of useful features.


On the backend Ketcher 2.0 uses Indigo Service

You can already try the Ketcher 2.0 demo But please be informed, that it is unstable and not all browsers are supported


Look at the Downloads page for the installation package and a sample Server v1 , Server v2 implementation.


Copyright © 2010-2019 LifeSciences unit of EPAM Systems, Inc.

Ketcher version 1.0 was released under GNU Affero General Public License v3.0 Ketcher version 2.0 was re-licensed under Apache License, Version 2.

This program is free software: You can redistribute it and/or modify it under the terms of the the Apache License, Version 2.0.

You should have received a copy of the Apache License along with this program. If you did not not, please see


Do you need assistance using our tools? Do you need a feature? Do you want to send a patch to us? Did you find a bug? Please use Github tickets package:

Commercial Availability

The Apache License v2.0 allows Ketcher to be used as a component in proprietary software products.

If the Apache License v2.0 does not fit your needs, please contact us to discuss the purchase of a commercial license. You may need the commercial license if you want to:

  • Receive ongoing support and maintenance

  • Design and implement custom changes for the structure editor

  • Do any other development/testing required for a proprietary software product

Visit our SolutionsHub page for more details