
[ TL;DR: solution to set firefox portable as the default html handler ]
Firefox Portable, and portable apps in general are great, but when it comes to setting firefox portable as the default html handler, or default internet protocol handler, the creators still haven’t found an integrated, in-app solution for doing that.
Sure, you can click on the “Make firefox the default browser” button, once you’ve loaded firefox portable, but that won’t actually set firefox portable as your default internet protocol handler, but instead, set the firefox app inside your portable firefox’s \App\ folder as the handler, which is not ok.
In other words, it’s not easy to make firefox portable the default browser on a windows system.
The default html or default internet protocol handler is the application that opens whenever you click on a link in an html file, or in another application, for instance, while you’re reading your e-mail using Opera Mail Portable, you’d like the links that you click on , in your e-mails, to open in firefox portable, instead of internet explorer and instead of the “stock” firefox, because once you’re using portable apps, it’s obvious, you want your interface, theme, font, language, bookmarks, passwords, and other personal settings, to load together with that program.
And if you’re simply clicking on “set firefox as the default browser” button to set the default handler, that won’t happen. So here’s what you need to do. There are 2 downloadable file sets at the end of this article, depending on whether you are using a portable firefox ESR version, or a simple one.
The two files inside any of the two sets will do the trick, but I’ll describe what the files do, so that you understand what is actually performed by using the solution shown here, and which one of them you need to download.
First and foremost, obviously, we are talking about a windows-based system here, and it’s presumed that you have full administrative privileges to execute the commands (the .cmd file). The command file will delete a few registry keys from the registry, and then load the second file, with the settings for the same registry keys appropriate for the firefox portable version you are using.
The registry key in both file sets presumes that you’ve installed your portable apps platform to “C:\PortableApps”. It also presumes that you’ve not set a custom path during the procedure of installing firefox portable, and the subfolder for firefox is “\FirefoxPortable” for the standard version, and “\FirefoxPortableESR” for the ESR (extended support release) version.
Please check your paths for the base portable app, and for the firefox portable’s location on your system, and TWEAK FIRST THE REGISTRY FILE after you’ve downloaded it, accordingly !
If your PortableApps location is something else then C:\PortableApps, then see that you change the registry key to reflect the right location. Also, please bear in mind, that the double backslashes in the registry file (“\\”), are not mistakes, but necessary, all in all, even if some of the syntax in the registry file seems odd, don’t modify syntax, just modify the location, the syntax is fine as it is.
Download the appropriate fileset from below to any folder you’d like, extract the files from the zip, and click on “ffportable_sethandler.cmd”. In only a second or so, it will execute both the registry key deletions, and the new registry key insertions necessary to set your firefox portable as the default html or default internet protocol handler.
It’s very easy to check if the operation was succesful, you can simply go to a cmd line (start->run->cmd and enter) , and type “start https://www.google.com” without the quotes. If the operation of setting the default html handler was successful, firefox portable will be loaded and google.com will load in the first tab. If not, either some error message will prompt you what’s wrong, or simply nothing will happen.
In case you weren’t successful in setting your firefox portable as the default internet protocol handler on your system, leave a comment and I’ll do my best to answer as soon as possible and help you. Of course, you’re also welcome to comment for any other reason you’d like.

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Thanks.
Fileset for firefox portable STANDARD version
(not ESR, usually installs in \PortableApps\FirefoxPortable)
Fileset for firefox portable ESR version
(usually installs in \PortableApps\FirefoxPortableESR)
Disclaimer: working with the registry can render your operating system unusable. Please understand that the solution provided here, is provided “as-is”, and I accept NO RESPONSABILITY either express or implied, for the solution’s effect on your computer.
You download and use the solution provided here, on your own responsability.