Email Preheader Tester
Type your subject line and preview text and see exactly where each inbox cuts it off — Gmail, Apple Mail and Outlook, desktop and mobile — so the words that matter never get truncated.
Cutoffs are approximate — inbox rendering varies by font, window width and settings.
The most-read copy you'll write is the part before the open
Every subscriber sees your subject line and preheader; only a fraction see anything else. That makes the inbox preview the highest-leverage copy in the whole campaign, and yet the preheader is the field most often left blank or filled with autopilot junk. When you don't set it, the client grabs whatever text comes first in your HTML — a hidden "view in browser" link, an unsubscribe note, the alt text of your header image. None of those earn the open. Treating the preview text as deliberate copy, written to extend the subject rather than echo it, is one of the cheapest open-rate gains available, and it costs nothing but attention.
Front-load, because the cut is unpredictable
The hard truth this tool makes visible is that there's no single length to write to — Gmail on a phone shows far less than Outlook on a wide monitor, and the same email looks different in each. Rather than chase one magic number, write so the essential message survives the most aggressive cut: put the hook in the first forty characters and let the rest trail off gracefully for clients that show more. A preview that still makes sense when truncated mid-sentence is doing its job; one whose whole point lives in the last few words is gambling on screen real estate you don't control.
AgentOutreach.io
One email is easy. AgentOutreach finds your ideal prospects and runs personalized outreach campaigns from your own inbox.
Frequently asked questions
What is an email preheader?
The preheader, or preview text, is the snippet of copy shown next to or beneath the subject line in the inbox before anyone opens the email. If you don't set one, mail clients pull the first text in your email body — often 'View in browser' or an image alt tag — which wastes valuable space.
How long should preview text be?
It varies by client and device, roughly 35–90 characters on mobile and up to around 140 on desktop. The safe approach is to front-load the most important words in the first 40 characters or so, and treat anything beyond that as a bonus that some clients will show and others will cut.
Should the preheader repeat the subject line?
No — that doubles your inbox real estate and wastes it. The subject line and preheader work as a pair: the subject hooks, the preheader extends or adds a second reason to open. Write them together so they read as one continuous thought rather than two competing ones.