I've used firebug in Firefox few times to alter the CSS of someone else's website - to make it more readable for myself in my own browser, by arranging the margins and making changes to elements other than just the text size. Is there a way I can permanently store this addition to the CSS for my own personal use, so that whenever I revisit the webpage, it will load the customized CSS styling in my browser?

Ideally, I would want to store only the additional CSS alterations I made, instead of essentially replacing what the website has with the version I modified - so that if they make changes, I don't end up keeping the old styling, and less of my customization breaks. I would also like the option of what URL filter I can use to decide which pages to optionally use my custom styling on.

I understand there might also be a solution where a browser script can be run which would insert a CSS rule into the webpage, but I have no idea how I would be able to accomplish that, so if that is an option I would like to hear more about how I could do that.


2 Answers 2


There is another add-on called Stylus which is a Stylish fork for Firefox, Chrome and Opera without analytics.

I wanted to update the answer to this question, because as of August 2017, Stylish has apparently become associated with tracking user browsing, and I'm concerned with it sending my browsing data to third parties.


I'm using the Stylish addon for that a long time already. As specified in your requirements, Stylish stores CSS within its own database, so your customized styles automatically get applied whenever you revisit the site/page. Moreover, it's very flexible and has a bunch of additional qualities:

  • rules based on domain, page, global or even the Firefox GUI
  • editor with error checking and more
  • integrates with UsetStyles.Org so you can install ready-to-use styles for many places

Stylish menu Stylish editor
Stylish context menu and editor (click images for larger variants)

As I wrote, I'm using this for many years now and could hardly do without. Strongly recommended :)

  • 1
    I've been using this for a while and it's amazing! Thanks for the reccomendation =)
    – Pie222
    Commented Mar 3, 2017 at 23:25

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