Mobile Email Preview.

No. It is accurate for width, line wrapping and the rules each app is documented to apply, but not pixel for pixel. Each app uses its own fonts, spacing and dark-mode colours, and Android phones change width with the Display size setting. The two invert views in dark mode are approximations and are labelled that way. For a final check, send yourself a test, or run an inbox placement test to see the result in real mailboxes.

There is no fixed number. How much of a subject fits depends on the phone's width, the mail app and the reader's text size. Type your subject in and the preview cuts it where our inbox layout would, tells you how many characters show, and on how many of seven phones it fits in full. Put the words that make someone open the email first, so a cut costs you nothing.

Preview text is the line an inbox shows after the subject. If you don't set one, the app fills it with the first text in your email, which is often a view-in-browser line or an image's alt text. You set it with a short line at the very top of the body, hidden with CSS. If it is shorter than the space available, follow it with spacer characters such as ‌  so body text doesn't creep in. The preview shows which text the inbox will use.

Choose a dark appearance in the preview. Your Dark Styles applies the CSS you wrote inside @media (prefers-color-scheme: dark), which is how Apple Mail and the Outlook apps handle it. The Gmail apps ignore that CSS and recolour the email themselves: Gmail for Android inverts light backgrounds only, and Gmail for iPhone inverts everything. Our partial and full invert views approximate those two treatments, so a test send is still worth it.

On phones, Apple Mail on iOS 13 and later, the Outlook apps for iPhone and Android, and Samsung Email 6.1 and later apply @media (prefers-color-scheme: dark) rules, according to the caniemail support tables. Gmail does not, in its iPhone app, its Android app or on the web. Yahoo Mail and AOL rewrite the media query so it never matches. For Gmail readers, pick colours and logos that still read when inverted, such as a logo on a transparent background.

Gmail cuts off emails whose HTML is larger than about 102 KB and puts the rest behind a View entire message link. Google does not publish the exact limit; 102 KB is the figure email testing vendors measure. Anything after the cut, often including the unsubscribe link, stays hidden until the reader clicks. The preview shows your HTML's exact size in bytes, and removing unused CSS, comments and repeated inline styles is usually enough to get under it.

Images linked from a server do not count, because the email only carries their address. What counts is the HTML itself: tags, inline styles, style blocks, comments and text. An image embedded as base64 data counts in full, and the Gmail apps do not display data: images anyway. Emails sent through SendCanyon are slightly larger than what you paste, because tracking and unsubscribe markup is added when each email is sent.

By default, yes. Gmail has shown images automatically through Google's image proxy since 2013 on the web and early 2014 in its apps, Outlook for iPhone and Android loads them unless the reader turns on Block External Images, and Apple Mail loads them. Readers can still switch images off, so turn them off in the preview too. Every image should have alt text, and the email should make sense when only the alt text shows.

Yes, it is free. When you check an email, we keep it and its result for 90 days, along with your IP address and browser, to prevent abuse, and then delete them. Your email is never sent to anyone. Images load from their own servers only when you turn images on, and nothing in your email can run scripts or submit forms inside the preview.