Yom Kippur is a solemn and reflective holiday, so it is not customary to greet those observing with "Happy Yom Kippur". Instead, appropriate greetings are more about meaningfulness and reflection. Here are some traditional Yom Kippur greetings:

• "Have an easy fast"
• "Good Yuntif" (Yiddish for "Have a good holy day")
• "Yom Tov" (Hebrew for "Have a good holy day")
• "Gmar hatimah tovah" or "Gmar tov" (Hebrew for "a good seal")
• "Shana Tova" (Hebrew for "Happy New Year")

Other greetings that are appropriate for Yom Kippur include:

• "Wishing you a meaningful Yom Kippur"
• "Have a blessed Yom Kippur"
• "May your sealing be sweet"
• "Have a good final sealing"
• "Have a good year" (can be used during the entire season)

It is also common to wish someone an "easy fast" in Hebrew, which is "Tzom kal".