Remembering Tony Krueger, creator of Word's spell-check squiggles
Original: In memory of the man who put red and green squiggles under words
Why This Matters
Established user interface pattern for real-time error detection adopted industry-wide across word processors and applications.
Microsoft developer Tony Krueger, who pioneered the red and green squiggles under misspelled words in Word, has passed away. He worked on multiple versions of Word and created the non-blocking spell-check feature that became standard in word processors.
Tony Krueger, a Microsoft developer, is remembered for his foundational work on Microsoft Word across multiple versions including Word 1.0, 1.1, 2.0, Word for OS/2, Word for Mac, and Word 6.0 and beyond. While he is credited on Wikipedia for porting Chip's Challenge to Windows for the Windows Entertainment Pack, his most impactful contribution was revolutionizing the spell-check experience. Early Word versions required users to explicitly trigger spell checking, which blocked document interaction while the program searched for errors. Krueger enhanced the Auto Spell Check feature to run non-intrusively during idle time, and crucially implemented real-time visual feedback by drawing red squiggles under potentially misspelled words and green squiggles under grammatical errors. This innovation prevented the blocking behavior that had caused users to disable the feature. Krueger's red and green squiggles became ubiquitous across nearly every word processor and many other applications. His work was so recognized that magician Penn Jillette enthusiastically praised the feature when learning of Krueger's involvement, and the squiggles appeared in 'Weird Al' Yankovic's parody video 'Word Crimes'. Today, red, green, and blue squiggles remain standard spell-check indicators across digital writing tools.