There are various solutions to use a software without having to install it, for example if you are working from a computer that is not your own: the most common is to use portable software, but versions of this type are not always found, and when they are available it can be difficult to keep them up to date.
Downloading Portable version software
A portable software is a program that must not be installed on the computer where it is used, just copy it to any folder, or a pendrive, and start it.
The main advantages are that it does not "dirty" the operating system where it is used, you can try to use it on computers where you do not have the permissions to install anything, just have a large enough pendrive and you can fill it with programs that can do almost anything, so you can go to your friend / customer and start the browser you like best with all the favorites you need, burn, check for problems in his operating system, all without installing anything on the computer.
The only (minimal) disadvantages, in case of using portable software, are that you may have to manually associate the type of file that the program can open or create shortcuts in the Start menu or on the desktop.
So summarizing you can either download the software in Portable version (usually on the download page it is specified), or you can copy the software installation folder and paste it on your pendrive.
Using the ZeroInstall program
It happens very often, however, that certain programs do not provide the software in a portable version.
In these cases, a lightweight and very easy to use program intervenes.
Download and extract this zip package on your Desktop.
Once extracted, run the "zero-install.exe" executable and wait for it to finish the initial configuration.
Once finished, you will find a huge list of software that you can download completely free (open-source programs).
One once you have found the software, click on "Run" and wait for the program to finish downloading.
The program feed is constantly updated, so many programs (free and open source) that you don't see currently on the list will be added in time very short.