Quick answer: design email headers at 600 pixels wide and 80–200 pixels tall, export the file at 1200 pixels wide for retina, and keep it under roughly 100 KB. Email has no owning platform and no official spec, but 600 is the width every template and inbox assumes.

Why 600 pixels

Social platforms publish exact pixel dimensions because they own the display surface. Nobody owns email. The 600-pixel width is a convention hardened by years of Outlook rendering: the Windows Outlook client uses Word's rendering engine and breaks layouts wider than the reading pane, while 600 scales cleanly on phones and sits centered in wide desktop windows. Gmail, Apple Mail, and the mobile clients all handle 600 without horizontal scrolling.

The size table

Asset Display width Export (retina) Height Notes
Logo / slim header 600 px 1200 px 70–150 px No navigation
Header with navigation 600 px 1200 px up to 200 px Logo plus links
Hero banner 600 px 1200 px 300–600 px Campaign hero
Full-width story image 600 px 1200 px 300 px 2:1 common
File size — — — Aim 40–100 KB; Gmail clips at 102 KB total

Retina export, not retina display

The trick that trips people is two separate numbers: the image displays at 600 pixels, but the source file should be 1200 pixels wide. On a high-density phone, a 600-pixel file displayed at 600 gets upscaled and looks soft; a 1200-pixel file constrained to 600 in the HTML stays sharp. The HTML does the resizing — you set the width attribute to 600, and the inbox handles the rest.

Height matters more than people think

Every pixel of header height pushes the actual message and the call to action below the first screen, and most commercial email is read on a phone. A header that exists only to carry the logo belongs in the 70–150-pixel range. The 200-pixel ceiling is for a logo row with navigation. Hero images (600×300 to 600×600) are a different asset — they are part of the campaign, not the standing header, and they earn their height because they carry the message.

File size and clipping

Gmail clips an email when the full HTML exceeds roughly 102 KB and hides the rest behind a "View entire message" link — which also breaks open-pixel tracking and hides the unsubscribe area. A single bloated header image will not trigger it alone, but a 400 KB header plus a 500 KB hero will. Aim for 40–100 KB per header image; JPG quality 80 for photos, and compressed PNG for flat logo artwork.

HTML vs. image-only headers

Where possible, build the header as HTML with a live logo image rather than one flattened image. Text on an image disappears when the inbox blocks images, and image blocking is still common. An HTML header with the brand name in text renders something usable before images load. The 1200×630 rule for social cards does not apply here — that is the Open Graph image world, not email.

When a campaign needs the full set

Product launches that combine email and social need a 600-wide header and hero, a 1.91:1 link card, and feed images, all from the same brand system. The ratios are not interchangeable, and resizing a link card into a 600-wide header is where text gets clipped. Neatico can produce the email header, hero, and the social variants together from one product description.

Frequently asked questions

What is the standard email header size? 600 pixels wide, 70–150 tall for a logo header and up to 200 with navigation. Export at 1200 pixels wide for retina and constrain it to 600 in HTML.

Why does my email look blurry on mobile? The source file is only 600 pixels wide. Upload 1200 pixels wide and set the display width to 600 in the HTML.

Can I make my email wider than 600 pixels? Some builders default to 660, but 600 is the safe width across Outlook, Gmail, and mobile. Anything wider risks clipping or scrolling in the worst clients.

What file size should an email header be? 40–100 KB is the target. Gmail clips messages around 102 KB total, so keep all images lean, not just the header.