Update April 2019: Thought I would add that for Firefox 63+, RSSPreview also allows you to preview a feed directly in Firefox and view it’s source code if you want. In order for this to work, you would need to select RSS for the Subscribe Using option in Awesome RSS‘s options.

Update December 2018: For Firefox 63+ they’ve removed most of the RSS handling code and adding these about:config entries don’t do anything now. See: Mozilla plans to remove RSS feed reader and Live Bookmarks support from Firefox – gHacks Tech News. Using Awesome RSS still works though.

Update November 2017: For Firefox 57+ there is now the Feedly Subscribe Button or Awesome RSS extension (which now has a Feedly option). The about:config modifications shown below also still work to add it to Firefox’s list of handlers.

Update November 26, 2013: Feedly changed their URL. They took “cloud” out of the URL. So, the correct URL is now: http://feedly.com/#subscription/feed/%s which I have altered below.

Update July 3, 2013: After reading How to add web services to the RSS signup page? on the mozillaZine forum (and comments below), thought I would put what needs to be done for Feedly here (after they finish re-doing the Firefox extension, none of this should, hopefully, be necessary):

To add a feed handler manually,

1. Type about:config in the address bar and press Enter.
2. Press the big button to bypass the warning.
3. In the search bar, paste browser.contentHandlers.types. and note the highest number of the preferences listed (e.g. browser.contentHandlers.types.5.title)
4. Right-click somewhere in the lower pane and choose New, then String.
5. Create preferences with the following values, replacing 6 with the appropriate number in your case. %s is a placeholder for the feed’s URL; Firefox will send that URL to the feed reader website.
   • browser.contentHandlers.types.6.title Feedly
   • browser.contentHandlers.types.6.type application/vnd.mozilla.maybe.feed
   • browser.contentHandlers.types.6.uri https://feedly.com/#subscription/feed/%s
6. Restart Firefox for the changes to take effect.

You should now see a Feedly option in your drop-down list for feed readers. 🙂

Update June 25, 2013: Thought I better update this post. Currently Feedly is up to version 16.0.528 of the Firefox extension and I am now running Firefox v22.0. Also, it looks like my account is now completely handled by the Feedly Cloud. As such, my URL to add a RSS feed into Feedly has changed from what is used below. The current URL which I now use when making the bookmark is: http://cloud.feedly.com/#subscription/feed/%s . It also seems like the extension is more of a front-end to the web only version of Feedly that adds some additional abilities over the website by itself. Hopefully this helps others that have been completely moved over to the Feedly cloud. 🙂

Update March 28, 2013: Feedly just released version 14.0 of the extension for Firefox on their site. It does seem to correct the problem with adding new feeds and does seem to fix the Google+ button issue when trying to share with it. It’s got some of its own little quirks (which some may not even notice). Version 10.2 is still available on the Firefox Add-On site (actually, they keep most of the older versions archived).

As most are aware by now, Google has announced that as of July 1st, Google Reader will be shutdown. I have been testing out Feedly as a replacement. If you’re reading this then odds are that you’ve already installed the Feedly Extension for Firefox. At the moment it’s basically a front-end for Google Reader and syncs its content with Google Reader. Changes made in Feedly will appear in Google Reader and visa-versa. More information can be found here on Feedly’s blog: Transitioning from Google Reader to Feedly.

The biggest problem that I and many others have run into is adding new feeds directly into Feedly. The normal process in Firefox usually displays an error like this. Anyway, here’s the easiest way that I’ve found to do it.

First, create a new bookmark of one of your existing Feedly pages or just make a new bookmark of anything really. Then, right-click the bookmark and select properties so that the following dialog is shown:

Like I’ve done, change the Name to something more meaningful, and most importantly, change the Location to http://www.feedly.com/home#subscription/feed/%s be sure to add the “%s” at the end. Then add a keyword, such as “f” like I have done, and click Save. (Note: see the June 25th update at the beginning of this post for the current URL if you’ve been moved over to the Feedly Cloud.)

Now, simply preview the RSS feed you want in Firefox using the normal method or copy the link to an RSS feed. Then in the address bar, either insert a “f(space)” (or whatever keyword you decided on) in front of the URL if it’s already showing or type “f(space)” followed by the URL to the RSS Feed:

After pressing enter, you should see the new page being displayed within Feedly’s context. At this point, just click on the green +Add button:

Success!! 🙂 (oh, as of this writing I am using Firefox v19.0.2).

Update March 17, 2013: Another work-around is to simply refresh the browser using F5, the address bar’s refresh button, or Feedly’s circular arrow refresh button, if you see that unable to load feed error page. After refreshing it seems to properly decode the URL and display the appropriate content to then add.