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How can I make Firefox use another installed Java runtime version?

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  • آخر ردّ كتبه sixtiek

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For development purposes I have several Java runtime versions on my Windows 7 64 bit machine. I try to keep the number of installed JDKs and JREs to a minimum and I want Firefox to use JRE 1.7.0_21 (32 bit) since this came with a JDK version I am forced to use for another application.

Firefox however uses JRE 1.6.0_31, and correctly reports this as insecure. It offers me the option to upgrade, but I do not want to download and install another JRE since I already have said JRE 1.7.0_21 installed. I would highly prefer to just be able to point Firefox to that JRE. I don't see an option to select another installed JRE however.

I have already attempted to manually modify the pluginreg.dat file (I know, it says Do not edit...) by changing the JRE 1.6 entries to JRE 1.7, but upon restart my edits were overwritten and the old JRE was back. As a result I cannot view certain web sites (also corporate/internal) without having to switch to lesser browsers.

Please let me know how I can make Firefox use the already installed JRE 1.7.

Chosen solution

Firefox scans the registry to find the location of the plugins. If Firefox finds one plugin and not the other then this means that the other Java plugin doesn't have a corresponding registry key.


64 bit Windows: HKLM\Software\Wow6432Node\MozillaPlugins\@java.com/JavaPlugin,version=xx.xx.xx 32 bit Windows: HKLM\Software\MozillaPlugins\@java.com/JavaPlugin,version=xx.xx.xx

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Chosen Solution

Firefox scans the registry to find the location of the plugins. If Firefox finds one plugin and not the other then this means that the other Java plugin doesn't have a corresponding registry key.


64 bit Windows: HKLM\Software\Wow6432Node\MozillaPlugins\@java.com/JavaPlugin,version=xx.xx.xx 32 bit Windows: HKLM\Software\MozillaPlugins\@java.com/JavaPlugin,version=xx.xx.xx

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Thank you for your response, cor-el. I was able to successfully add the JRE 1.7 plugin to Firefox by modifying the existing JRE 1.6 registry entries, but I would not recommend this procedure to users that are less confident in registry editing. Too bad there is not a more user friendly way to do this.

Unfortunately the Java applet I'm trying to view is still not displayed. I've dug a bit deeper and found that the applet explicitly specifies an older JPI version (1.5.0_02). AFAIK Firefox cannot deal with this if its installed JPI (now 1.7.0_21) does not match the version requested. So either I'm going to have to dig up this older JPI version and install that too, or just switch to an alternative browser to be able to view this applet.