The following is a list of extensions whose functionality overlaps with functionality possible with user styles and Stylish. User styles will often use less system resources and provide more customizability than dedicated extensions. If you know of other extensions that can be replaced by user styles or if this list misrepresents something, feel free to mail me.
| Extension | Description | Replacement | Caveat |
|---|---|---|---|
| Adblock Plus with FiltersetP Updater | Blocks ads | Ad Blocking FiltersetP user style | The style does not block the content from loading, while the extension gives this option. |
| Greasemonkey | Allows running of custom JavaScript on websites. | Many user scripts can be replaced by user styles, which perform better. | User styles cannot add content, user scripts can. User scripts also allow for more finetuned application. |
| Remove It Permanently | Allows removal of certain elements of a page. | User styles can equally remove elements of a page. | Remove It Permanently makes it easier to choose the elements remove, especially for people who don't know CSS. |
| Customize Google | Allows filtering of Google results, among other things. | Google Search Results Filter user style. | Customize Google makes it easier to add or remove things to filter. It also has other functionality. |
| WellRounded | Rounds form controls in the Firefox toolbar | WellRounded user style | |
| Slim Extension List | Compacts Firefox's extension list | Slim Extension List user style | Slim Extension List has other functionality. |
| URI id | Puts an id attribute on documents loaded so that userContent styles can apply to just them. | -moz-document rules used by Stylish completely negates the need for the id attribute. | |
| Stop-or-Reload Button | Combines the Stop and Reload buttons. | Combine Stop/Reload buttons user style. | |
| FAYT | Restores the Firefox find toolbar to 1.5 functionality. | FireFox - Find Toolbar same as FF1.5 user style. | |
| OpenBook | Automatically shows the folder tree in the add bookmark dialog. | Add Bookmark Dialog: Show Folder Tree user style. | OpenBook has other functionality. |
| TargetAlert | Adds file type icons to the end of links. | Link Warning user style. | |
| Fitts' Back Button | Makes the Back button larger for easier clicking. | Fitts's Back Button user style. | |
| Separe | Puts blank tabs as separators between tabs. | Tabs - add dividers like Séparé user style. |