Subject Line & Deliverability Tester
Test your subject line length, emoji count, and spam keywords before sending.
Suggested Preheader Text for Your Subject Line
Pair your subject line with one of these complementary preheader snippets to boost open rates and maximize inbox preview impact:
6 Battle-Tested Tips for Higher Email Open Rates
Proven best practices to get your emails noticed and opened in crowded inboxes.
Target 30 to 50 Characters
Over 60% of emails are opened on mobile devices where long subject lines get truncated. Keep your core message early in the line.
Front-Load Key Value Words
Place your most intriguing word or benefit at the beginning so fast scrollers catch the value proposition instantly.
Avoid Spam-Flag Trigger Words
Words like "100% free", "guaranteed", "$$$", or "act now" trigger automated ISP spam filters and lower deliverability.
Use 1 Strategic Emoji
A single relevant emoji can increase open rates by up to 15% by standing out visually, but excessive emojis look spammy.
Always Write Preheader Text
Preheader text acts as a secondary subject line. Use it to expand on the subject line's hook rather than repeating it.
A/B Split Test Variations
Test question-style vs statement-style subject lines on a small sample segment before broadcasting to your full list.
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Frequently Asked Questions
Everything you need to know about subject line optimization and inbox deliverability.