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Mozilla added an option to recent Firefox Nightly version, version 69 at the time of writing, to enable Fission in the web browser.

I talked about Mozilla's ambitious Project Fission in February 2019. The organization is working on changing Firefox's current process model to improve performance, security, and stability of Firefox operations.

One of the core changes that Fission introduces is that any cross-site iframe will be loaded in its own process to separate it from the main content process of the loaded site.

Mozilla introduced Multi-Process capabilities in the Firefox web browser in 2016.

Firefox's new architecture resembles that of Google Chrome's. Google introduced site isolation support in the company's web browser in 2018. The company revealed in the meantime that the change had a positive effect on stability and security, and that it caused a 20% increase in RAM usage.

Mozilla is aware of the implications. Firefox would use more processes than currently as well and that would increase the browser's RAM usage and requirements as a consequence. The organization is working on memory optimizations at the same time to reduce that impact when Fission launches in stable versions of the web browser.

Firefox Nightly users may enable Fission already in the web browser. It needs to be noted that Fission is still an ongoing project and that bugs are to be expected at this point in time. Users may experience crashes when they visit sites and other issues while they browse the Internet.

It is therefore recommended to enable Fission only for testing purposes at the time. Users should also note that memory usage is higher than it will be when Fission launches officially. The memshrink project is still ongoing and many of the changes have not been implemented yet in the Firefox web browser.