A NARROW NO-BREAK SPACE (U+202F) will NOT stretch when justification is applied.

[r12a]

Test link(s):

test

Results:

• Gecko: ✅ Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:94.0) Gecko/20100101 Firefox/94.0
• Blink: ✅ _Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_157) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.55 Safari/537.36
• Webkit: ✅ _Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_157) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Safari/605.1.15

Related tests: Text alignment & justification