Let's try to build an answer with the full information here...
This is a known issue with Microsoft Update KB3013455, released on the 10th February 2015.
For a quick way to check if you have the update installed, open a DOS command prompt and type:
wmic qfe list brief /format:texttablewsys | find "KB3013455"
If this returns no text at all, the update is not installed; if it is installed, you'll see KB3013455
and more text printed out.
The issue can be resolved by either
uninstalling the update (but this will leave you with a security vulnerability). A reboot will be required.
Installing a subsequent update (the Microsoft official fix, released on the 18th Feb 2015):
To resolve this issue, install update 3037639. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
3037639 Fix for text quality degradation after security update 3013455 (MS15-010) is installed.
This fix will take you to a page where it seems you're downloading the original KB3013455 all over again. Keep going, when you actually click to download you will get an option to get the fix, KB3037639.
A reboot will be required.
The fix was later included in Microsoft's automatic updates in March 2015.
Edit the list below to add affected systems:
- Windows Vista SP2
- Windows Server 2003 SP2
- Windows Server 2008 SP2
- Windows XP (for people on the Custom Support Program that keep receiving patches for XP)
- Windows FLP
- Windows Embedded (WEPOS, POS Ready 2009)
Edit the list below to add affected Fonts (only some font sizes show problems):
- Arial
- Courier New
- Times New Roman
- many others
Description of the problem (from here):
Essentially the small fonts (8-20pt) that normally result in a one-pixel line (think of lowercase "b" or "t" or "d") would now be a random mess between 1 and 2 pixels. Turning on "Clear Type" or font smoothing does "smooth" the garbage and it doesn't look as awful but that doesn't make the text any more readable.
99% of those with font rendering problems all over their Windows O/S (like word in this case) only post about the appearance in their browser. It's now almost impossible to google for font rendering and find any page that doesn't revolve around browser font rendering technologies :( – ndemou – 2015-02-24T11:43:18.297
My initial posting did outline that fonts still looked fine in Word (for one) in the title of the question, but someone edited it to make it more generic. As a web dev though, yes, it was browsers that I mostly noticed the problem in. – Codemonkey – 2015-02-24T12:15:03.330
1Sorry for the bitter comment Codemonkey. I came here after googling with poor results for maybe half an hour and was in a bad mood. BTW if the same fonts/sizes that appear ugly in a browser appear OK in Word then the accepted answer is not for you because it's about a system-wide font rendering bug which should affect all programs. It's easy to get confused with so many "moving parts" that play a part in this problem though. I surely did. – ndemou – 2015-02-25T07:45:16.227
This was 100.0% the problem with my system @ndemou. It wasn't system wide, but it was unquestionably KB3013455 that was the issue. Uninstalled it and the problem went away. Reinstalled it and it came back, applied MS hotfix for it and it went away. I didn't try Arial/Courier/Times in Word though, it was Montserrat and Calibri which maybe weren't affected. The hotfix definitely fixed my browsers etc though. – Codemonkey – 2015-02-25T10:40:46.317
1I'm running into this issue in WIndows 10; the KB3013455 issue didn't fix it. – Turtles Are Cute – 2015-10-06T21:31:46.617