Why Your Email Signature Looks Different on iPhone vs Mac (and How to Fix It)
The signature that looks perfect on your Mac sends as a mess from your iPhone: giant logo, wrong fonts, missing image. Root cause: they are not the same signature — and the fixes follow from that.
Step by step
Understand: there are two separate signatures
Apple doesn't sync signatures from Mac to iPhone — iCloud only syncs them between Macs. Your iPhone sends whatever is in Settings → Apps → Mail → Signature on the device, which is often an old, mangled paste. First fix: make both come from the same source.
Put the SAME signature on the iPhone
Copy the identical HTML to the phone the reliable way — clean HTML with hosted images, not copied from an email (that breaks the images). The full method is in our iPhone guide; Autograph automates it with a QR code.
Fix the giant-logo problem
If your logo blows up to full width on phones, the image has no explicit dimensions. The HTML must set width/height attributes (and a max-width) so every client renders it at the intended size.
Fix the font-size drift
Signatures without explicit font sizes inherit each device's defaults — 13px on the Mac can become 17px-ish on iOS. Set explicit pixel sizes on every text element in the signature HTML.
Expect the Dark Mode illusion
In iOS Dark Mode your signature can look dark-on-dark or outright invisible in the composer. Recipients see the correct colors — verify with a test to Gmail before 'fixing' anything.
Test from both devices
Send yourself one email from the Mac and one from the iPhone, to the same Gmail address, and compare side by side. When they match there, they match for everyone.
One signature, both devices, one minute
Design it once in Autograph: one click installs it in Apple Mail, and Set up iPhone puts the identical signature on your phone via QR — sizes, fonts, and images intact.
Download Autograph free See the templatesCommon questions
Why doesn't Apple just sync signatures to iPhone?
Only Apple knows. iCloud syncs Mac Mail signatures between Macs; iOS Mail's signature is a separate on-device setting with no sync and no API. Every tool works around it — the difference is how well.
My iPhone signature has images that show as question marks — related?
Yes: that's iOS rewriting pasted images to dead internal references. Replace the iPhone signature using the clean-HTML method in the iPhone guide.
Do I need to design two signatures?
No. One well-built responsive signature (explicit sizes, max-width, stacking for narrow screens) renders correctly from both — that's how Autograph's templates are built.