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It is harmless to download it and try it - if you have a 32 bit operating system, it won't run.
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However, Internet Explorer 11 is available in Windows 10 for use with Java. The Microsoft Edge browser (new in Windows 10) does not support Java. The HTML5 implementation of Jmol, JSmol, works just fine in Firefox.
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Until sometime in 2018, there was a special version of Firefox called Extended Support Release (ESR) that supported Java however, later ESR versions no longer support Java. That change happened in March 2017 and had been announced well in advance. The Mozilla Firefox browser does not support Java (including the Java-dependent version of Jmol) since version 52 of the 32-bit browser the 64-bit Firefox has never supported Java.
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The HTML5 implementation of Jmol, JSmol, works just fine in Chrome. This change happened in late 2015 and had been announced well in advance. The Google Chrome browser does not support Java (including the Java-dependent version of Jmol). Official browser compatibility documentation for Java. Java Applets do not work in Chrome, Firefox, Edge, or Opera
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1 Java Applets do not work in Chrome, Firefox, Edge, or Opera.
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