Flagship Subject Studio

Subject Line Tester & Generator

Score your subject lines, test mobile inbox preview cutoffs, and generate high-open variations.

Test Examples:

How It Works in 3 Simple Steps

01

Enter Subject Line

Type your proposed subject line.

02

Score Open Rate Potential

Analyzes brevity, curiosity, punctuation, and capitalization.

03

Mobile Preview & AI Ideas

Preview desktop and mobile truncation limits, plus get 4 instant optimized variations.

Pro Tips for Maximum Performance
  • Avoid exclamation marks, questions marks, and words like "FREE" or "Opportunity".
  • Reference a specific trigger: "idea for [company]", "quick question [first_name]".

Frequently Asked Questions

Between 15 and 35 characters (2 to 5 words). Short subject lines look conversational rather than promotional.

Lowercase or sentence case ("quick question about inbound") gets significantly higher opens than Title Case.

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Want Guaranteed Pipeline Without Running Tools Manually?

Koravio builds, verifies, and runs end-to-end autonomous outbound infrastructure that books 15–30 qualified B2B meetings per month on 100% pay-on-performance.

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