Email Preheader Optimizer
Your preheader is the second thing recipients read — and most ESPs cut it off at 90 characters on mobile. Paste yours and see exactly how it appears in Gmail on desktop, iOS Mail, and Android.
Length Analysis
Type something...Inbox Preview Simulation
Quality Signals
Email Preheader Best Practices
How long should an email preheader be?
40–130 characters is optimal. Most email clients show between 75–130 characters depending on device and screen size. Mobile clients typically truncate at 90 characters.
What happens if I don't set a preheader?
Email clients pull the first visible text from the email body — often "View in browser" or blank whitespace. This is a wasted opportunity to reinforce your message or build curiosity.
Do preheaders affect deliverability?
Not directly, but spam words in preheaders contribute to content-based spam scoring in SpamAssassin and similar engines. Clean, relevant preheaders are safer.
What's the difference between preheader and preview text?
They are the same thing. "Preheader" refers to the HTML element; "preview text" is what recipients see in their inbox list view below the subject line.
Related tools:
Why We Built This Tool
Most ESPs don't show how preheaders render across different email clients. Gmail shows ~130 characters; Apple Mail shows ~75 on desktop but only 30–40 on mobile. Teams write 150-character preheaders thinking they're optimized, never knowing mobile users see only 'Act Now! We have a special...' and miss the real message. This tool surfaces truncation across all devices before send.
What Goes Wrong Without This
Preheader truncation wastes copy. A perfectly crafted 120-character preheader means nothing if mobile users see only the first 40 characters. Teams don't catch this until campaigns are live and engagement data surfaces. Visual previews prevent wasted send-time optimization.
Who This Tool Is For
E-commerce & DTC Brands
Marketing teams optimizing promotional preheaders to complement subject lines and drive opens on high-volume campaigns to subscribers.
Email Marketing Agencies
Teams testing preheader copy across clients and industries — validating that preview text matches the subject line promise before sending.
B2B SaaS & Outbound Teams
Product and notification teams crafting preheaders for transactional and sales emails that reinforce subject lines without triggering spam filters.
Frequently Asked Questions
How long should an email preheader be?
What's the difference between preheader and preview text?
Do preheaders affect deliverability or spam scoring?
Do I need an InboxEagle account to use this tool?
Optimized Preheader, Broken Deliverability — Don't Stop Here
A strong preheader improves open rates once your email reaches the inbox. InboxEagle measures whether your emails are reaching the inbox at all — with real seed mailbox testing across Gmail, Outlook, and Yahoo. If your open rate is low, you'll know exactly why.
Start Free 14-Day TrialNo credit card required · Cancel anytime