Try this article for a link to the installer for your OS: Install an older version of Firefox.

If you install Firefox 21 it is unsupported and insecure as explained in the linked article. There is an alternative that you may wish to consider.

Initially this sounds crazy but read what I say and see if you agree with my logic.

Instead of running the Firefox Release (Currently Firefox 22) and not having any secure downgrade option why not jump ahead to the Firefox Beta. The Beta is pretty stable and becomes the Release Version after six weeks of trial.

Should you have problems with Firefox Beta (Currently Firefox 23) install the release over the top of it and thus downgrade. That downgrade is to a secure and supported version. You know it will work (once you have been on the Beta channel a few weeks) as it was the version you used previously because it was the Beta six weeks before.

If there are problems you discover them six weeks earlier, and so have six weeks to find a solution, or wait for a fix, and meanwhile the option is to downgrade to instantly resolve the issue.

Information about the Beta with a download option

• http://www.mozilla.org/en-US/firefox/beta/

Before dismissing the idea of using Beta software; please remember that the changes and risky testing takes place in the Nightly for six weeks, then the less risky changes in Aurora for a further six weeks. There are two versions prior to the Beta that is why the Beta may be expected to be very close to the Release and as I say fairly stable.

• a notable blog about the rapid release cycle
  https://blog.lizardwrangler.com/2011/08/25/rapid-release-process/
  Note A lot of the teething troubles, for instance add-on compatibility issues have been resolved since then

Thanks for your answers, but I think I should have been more descriptive of my concerns. I have read several reviews of Firefox V22, which complained of blurry rendering and irreversible new features. I'm quite happy with my current version 21. I'd like to upgrade to version 22, but would also like a downgrade path if I suffer issues with it. Using Beta versions does not solve my problem, but it now appears, through esp, that my problem can be better defined. . .

• As policy, Mozilla does not provide an installable downgrade, even of one version past. I think this is the issue, and bad policy to boot.

If I'm wrong, I'd really appreciate someone pointing me to an installable download of version 21 so I can get on with the v22 upgrade in safety. Pointing me at the development directories does not get me an install for v21, and pointing me at Betas' get me far ahead of where I would like to be. I appreciate your ongoing advice, and I feel that my concern is prudent. Further discussion, perhaps leading to a method to downgrade if necessary is much implored. -ss

Hi ssprinz, I gave you a good link for Firefox 21.

Regarding the possibility of "blurry rendering" in Firefox 22:

If you run Windows, then Firefox will now use your Windows DPI setting to scale the user interface and content. For example, if you set Windows to use a font size of 125% (DPI of 120), then the content in Firefox will be zoomed by 25% automatically. Also, unlike in the past, icons on toolbars will be zoomed by 25% (the menu and toolbar text should be the same as before, although this may vary depending on your Windows display settings).

As always, there are several approaches to tailoring Firefox 22 to your tastes, but completely turning off this new approach to scaling isn't available.

If you use the Beta version there is then a secure downgrade option: the Release.

As for failing to provide a secure downgrade from the release part of the problem is that any security fixes in the new release are publicised. That increases the risk that the security holes in the outdated version will be exploited. See https://www.mozilla.org/security/known-vulnerabilities/firefox.html

We do provide a link to previous version installers but recommend against using them.

Most improvements or changes will be disliked by some users. We need to remember Firefox works on a variety of display and device types with screens ranging from tiny to very large. That now needs to include the Hi Dpi large screens supported by modern Windows & Mac Retina.

This forum is for users helping other users. We try not to discuss development issues and development decisions.You may find a forum where such discussion could be on topic

• trawl through http://www.mozilla.org/about/forums/#general-development
• Or to make a comment use https://input.mozilla.org/en-US/feedback (From the Release, not fx21)

Thanks again for your prompt responses. Mr. jscher2000 gave me the link to the first page I saw while researching this issue. While it does offer a download of Version 20.0.1 or Version 3.6 (which must be really older), it does not offer an install of my current Version. Not a good link for Firefox 21.

I do, however, appreciate the explanation of Windows DPI and on investigation my Windows 8 reports 'making everything on my screen bigger is unsupported by my monitor'. Meaning, its probably a non-issue (for me).

Mr. John99 really makes the point about published security vulnerabilities in Version 21. That's really the motivator. I would like to point out I'm not resistant to change. I want to follow upgrade paths. I just would like to do so prudently.

• Regarding the issue of 'blurry rendering', there is a lot of negative review on this issue, and I think a more thorough discussion somewhere near the front support pages would quell my misgivings, and perhaps others ' reading the dire reviews. Blurry rendering deserves a clear explanation.

Thank you both for your insight and I will now jump without proverbial parachute. If I find Version 22 to be a no brainer I will take your advice and join the beta crew. -ss

Hi ssprinz, the "older version" page adapts to the version you are running. After installing Firefox 22, it should show you a link for Firefox 21.

Hello again ssprinz,

While it does offer a download of Version 20.0.1 or Version 3.6 (which must be really older), it does not offer an install of my current Version. Not a good link for Firefox 21.

The article you read Install an older version of Firefox like most of our kb articles is interactive. If you view it from Firefox 21 it offers Firefox 20, if you view it from Firefox 22 it offers Firefox 21 installer.

You also have two selector buttons on the article and may manually change which OS & Fx you want information about.
Note if you do manually change views you may need to clear the for_os or for_browser cookies to see the correct default next time you visit an article.

Fx 3.6 was prior to the rapid release cycle, it had point releases, and was supported for quite a long time.

Regarding the issue of 'blurry rendering', there is a lot of negative review on this issue, and I think a more thorough discussion somewhere near the front support pages would quell my misgivings, and perhaps others ' reading the dire reviews. Blurry rendering deserves a clear explanation. 

Note the forum homepage for Firefox (Desktop)

• /products/firefox
• Has Hot Topics section that includes a link to
  Webpages are large and blurry after updating Firefox - how to fix

Take care if changing versions or channels of Firefox. You do not even normally need to uninstall the old version. Do NOT use any option to remove personal information, because that destroys bookmarks and passwords.

Hello,

I am using Windows XP (sp3) on an older laptop. Am I going to run into any known problems when updating to FF 22.0?

Thanks!

Hi Jeswondrin, I'm not aware of any special issues with Windows XP and Firefox 22.

If you run ZoneAlarm, then you may encounter an issue with intermittent copy failures (trying to copy may clear the clipboard but not add the new text).

See also this thread created by Jeswondrin.

• [/questions/965132]

It may be best to continue the discussion there.

That information would have been more helpful in my earlier attempts to locate a downloadable V21.

Thanks so much, jscher2000! Good to know. I posted my question here after reading this thread, but it was also relevant to another thread I had already started, so I reposted it there as well (cor-el's referenced link). Both sets of feedback were informative -- thanks to both of you.