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Every broken-looking signature is a wrong-sized image. The exact dimensions that work in Gmail, Outlook and Apple Mail.
Display 90–120px wide · export @2x (180–240px) · PNG with transparency.
Display 70–90px square · export @2x · JPG, face-centered crop.
600×200px (or 700×150 slim) · <100KB · link it to a landing page.
Keep the whole signature ≤600px — the standard email content width.
Export images at double their display size and set explicit width/height in the HTML (e.g., a 240px-wide logo displayed at width='120'). Screens render it crisp; file size stays sane if you compress. Keep every image under ~100KB and the whole signature under ~300KB — heavy signatures get clipped by Gmail.
PNG for logos, icons and anything with text or transparency; JPG (quality ~80) for photographs. Skip GIF except for intentionally animated banners — and if you want one, our AI Banner Maker exports correctly-sized static PNGs and looping GIFs for email.
The rule that trips people up most is that a signature image needs two sets of dimensions: the size it is displayed at, and the size the file actually is. On high-DPI screens — every modern phone and most current laptops — an image whose file dimensions match its display size looks noticeably soft. The fix is to export at roughly twice the display size and then constrain it with explicit width and height attributes in the HTML. A logo shown at 150px wide is exported at about 300px and set to width=“150”. This costs a little file size and removes the blurriness that makes an otherwise good signature look amateur.
Crisp edges on flat colour and text, and it supports a transparent background so the logo sits correctly on both light and dark backgrounds.
Headshots and photographic banners compress far better as JPG; a photo saved as PNG can be several times larger for no visible gain.
Support is inconsistent across clients — it may simply not render.
Some clients show only the first frame, so the first frame must make sense on its own.
Aim to keep total signature imagery well under a couple of hundred kilobytes. Heavy signatures slow loading and contribute to Gmail clipping long threads.
It prevents layout shift while images load and stops Outlook's Word engine resizing things unpredictably.
Dimensions only matter if the image loads at all. Signature images must be hosted somewhere publicly reachable over HTTPS, with no login required and no hotlink protection. The classic failures are linking to a file in Google Drive or Dropbox with restricted sharing, using an http:// URL that recipients' clients block as insecure, or embedding a local file so it travels as an attachment. Also remember that many clients block remote images by default, so your signature must still make sense with every image switched off — which is another reason the text should never live inside the picture. Diagnosis for broken images is in this troubleshooting guide.
Written and maintained by the ProSignature team. Competitor pricing and feature claims on this site are verified against each vendor's live page on the day of writing — last verified 26 July 2026. No affiliate links. How we work.
Design a branded signature and install it into Gmail automatically — free.
Create my signature — free600×200px is the safe standard (700×150 for a slim strip), under 100KB, exported at 2x for retina screens.
It's displayed at its native size on a retina screen. Export at 2x the display size and set the display width in the HTML.
600px — beyond that, mobile clients force horizontal scrolling or shrink your design unpredictably.
Gmail clips messages (including signature HTML) around 102KB and lazy-loads heavy images — keep the signature lean.