ChemWidget FAQ

General Questions

Which browsers is ChemWidget compatible with?

ChemWidget will run in any modern web browser (including mobile): FireFox 3.6 or later, Google Chrome, Safari 5 or later, Opera 10 or later, Internet Explorer 9, as well as iOS and Android browsers.
We also provide legacy support for Internet Explorer 8. ChemWidget is fully supported and functional in IE8. While we do not recommend using IE8 for running ChemWidget, we understand that sometimes it is the only option. IE7 and IE6 are known to work, however, we do not provide support or fix any problems related to these obsolete browsers.

How big is the client download size?

The download size varies with the client browser. IE8 download is ~450K, while WebKit-based browsers download only about 350K.
Even for legacy Internet Explorer, the download size is rather small. It is comparable to a single mid-size JPEG image. The client browser will download ChemWidget scripts only once and store them locally. Re-download will be required only if the user explicitly clears their browser cache, or if a new version of ChemWidget is deployed to your website.

Using ChemWidget

How can I add an R-group or an element atom?

Click on the element pop-up toolbar, then enter the element or R-group symbol in the text box at the bottom and click “Add” or press Enter. ChemWidget supports nine types of R-groups (R1 to R9). Do not add spaces (R 2) or hyphens (R-2) to these symbols.

Building Sites and Applications

Is it possible to change the font that ChemWidget uses for chemical structures?

Yes, it is! Simply edit


and change cw_font_face variable to the name of desired font. The font name should be provided in the same format as you would do it in CSS, except it is not necessary to use single or double quotes around multi-word names. For instance, uses Lucida family for all chemical structures.

What JavaScript API calls does ChemWidget provide?

ChemWidget API is documented in the user manual, which shall be available for download shortly.
The following API calls are considered stable and won’t change in the future ChemWidget releases:

initViewer(divID, width, height, displayName, displayFormula, displayMw)
initEditor(divID, width, height)
setMolFile(divID, molFile, molName)
setMoleculeName(divID, molName)

Licensing and Maintenance

What types of licenses do you offer?

Our basic type of license is the single-site license. It permits you to use ChemWidget on a server identified by a single hostname or IP address (for example, “”). You can use ChemWidget on an unlimited number of pages, as long as they are served from that specific address.
To address the needs of our customers who use ChemWidget for building intranet applications, or need to deploy to multiple servers at once, we offer a multi-server universal licensing option.
ChemWidget is also available as a Vaadin widget. The terms of Vaadin widget license are the same as for the multi-server license, except it also grants access to the core source code. This requires an NDA agreement to be signed.
Please contact our sales team to receive a quote for a multi-server or a Vaadin widget license.

Do you offer evaluation or trial licenses?

Yes, we do!
Please contact us for details. You will be free to evaluate ChemWidget without any time or functionality limitations.

Our server address has changed. Do we need to buy another license?

Not necessarily.
For every single-server license, we will allow up to three hostname changes while you have an active maintenance contract. If the hostnames change frequently in your deployment scenario, you might want to think about purchasing a multi-server license.