Apple Mail · iPhone · Subject line
About 48 characters show on an iPhone 14. Modeled as a pixel box calibrated to the character count seen on the device, so wide and narrow letters are handled.
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On some iPhones, Apple may show its own short summary instead of your preview text. Your subject line is the part that always shows, so make sure it works on its own.
In the Mail app’s inbox on iPhone the subject sits on one line under the sender, and iOS cuts it with “…” at the screen edge.
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About 48 characters (354px). About 48 characters show on an iPhone 14. Modeled as a pixel box calibrated to the character count seen on the device, so wide and narrow letters are handled.
On iPhones with Apple Intelligence, Mail can show a short AI summary instead of your preview text. The subject line still shows as written, so it has to carry the offer on its own.
Apple Mail · iPhone still shows it, but cuts it with “…”, and anything past the cut is invisible to most people.
This screen cuts by width, not characters. Wide letters like W and M use up to four times the room of i or l, so two texts of the same length can be cut in different places.