Google Chrome
Here are the directions for how to update the Chrome application.
Mozilla Firefox
Here are the directions for how to update the Firefox application.
Microsoft Edge
Here are the directions for how to update the Edge application.
Apple Safari
Safari updates automatically whenever you update your MacOS.
Click Apple menu > System Preferences, then click Software Update .
See here for more, including specifications for particular MacOS versions. If you have an older OS, this resource has more directions on how to maintain it as best you can, or even upgrade it to newer OS's.