How to enable stylistic sets

Stylistic sets allow you to access additional, optional parts of the font on a per-feature basis. In Fira Code, they allow you to enable/disable alternative character variants.

Fira Code v2 supports these stylistic sets:

You can enable stylistic sets only if your editor supports it.

Atom

Go to Atom -> Stylesheet, add:

atom-text-editor {
  font-feature-settings: "ss01", "ss02", "ss03", "ss04", "ss05", "ss06", "zero", "onum";
}

Sublime Text

Go to Sublime Text -> Preferences -> Settings, add:

"font_options": ["ss01", "ss02", "ss03", "ss04", "ss05", "ss06", "ss19", "ss20"]

(for now Sublime Text does not allow you to specify zero and onum features, but they are repeated as ss19 and ss20.

VS Code

Via editing electron-browser/index.html, see https://marketplace.visualstudio.com/items?itemName=be5invis.vscode-custom-css

CSS

... {
  font-feature-settings: "ss01", "ss02", "ss03", "ss04", "ss05", "ss06", "zero", "onum";
}

Some Apple apps

Adobe apps, MS Word etc

https://www.macworld.com/article/3052388/how-to-access-advanced-opentype-features-in-a-variety-of-mac-apps.html