Free tool
Free Email Preview Text Tester
Type your subject line and preview text (preheader) and see exactly how the pair renders in a phone and desktop inbox - with character-count bands, truncation points, and the classic preheader mistakes flagged before you send. It runs entirely in your browser.
Runs entirely in your browser. Nothing is uploaded or stored.
How it works
The preview text - also called the preheader - is the grey snippet an inbox shows right after your subject line. Together they are the only two lines a reader sees before deciding to open, yet most senders write the subject carefully and let the inbox grab whatever comes first in the body: a logo alt text, "View in browser", or an unsubscribe link. That wasted line costs opens on every single send.
How to use it: type your subject and your preview text. The tool shows the pair as an inbox row at phone width (roughly 40 visible preview characters) and desktop width (roughly 90), marks exactly where each device cuts you off, and scores the snippet: is it missing, does it just repeat the subject, does it start with boilerplate, does it carry spam-trigger words or ALL-CAPS shouting? Every issue comes with a concrete fix. The device bands are honest working medians - real clients vary by viewport and font, which is why you see the preview instead of trusting a single number.
Write the preview text as the subject's second sentence, not its echo: the subject makes the promise, the preheader adds the detail that makes it credible - a number, a date, a name, the concrete thing inside. Aim for 40 to 100 characters and put the payload in the first 40, because that is all a phone shows. Pair this tool with the subject line tester for the line before the dash, and grab a proven starting point from our welcome email template if you are wiring up an onboarding sequence.
Preview text is one line of a bigger discipline: every email AutoEmail drafts is written per message in your voice and scored for spam and deliverability risk before it is staged for your approval - so the whole email, not just the snippet, is checked before anything sends.