Length optimization
Checks if your subject line is the optimal 3–7 words (under 50 characters) for maximum open rates and mobile preview.
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Enter a subject line to test.
Paste your cold email subject line and get an instant AI-powered score out of 100. The tester evaluates length, clarity, spam risk, personalization, and engagement – then generates 3 improved alternatives you can copy and use right away.
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Create a free accountChecks if your subject line is the optimal 3–7 words (under 50 characters) for maximum open rates and mobile preview.
Evaluates whether your subject line clearly communicates the email's purpose at a glance.
Scans for spam trigger words, excessive punctuation, ALL CAPS, and misleading patterns that hurt deliverability.
Assesses whether your subject line includes or suggests personalization opportunities for better engagement.
Analyzes curiosity, value proposition, and urgency to predict open-rate potential.
Get 3 improved subject lines that address specific weaknesses identified in your original.
Your subject line is the first – and often only – thing standing between your email and the trash folder. Get it right, and you earn an open. Get it wrong, and nothing else matters. Here's what the data from 31 million emails tells us.
A great subject line earns attention by feeling specific and relevant, not by trying to sound clever or urgent. Write it like it's for one person — because the best ones are.
Idea for {{company}}'s Q2 pipeline, {{first_name}}
Two personalized attributes, a concrete hook, and just the right length. It signals relevance without being pushy.
Quick question, {{first_name}}
Personalized, yes — but a pattern so overused it barely registers anymore. It opens without promising anything, which rarely compels action.
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Generic, impersonal, and sales-first. 65% of decision makers say cold emails fail because they feel too pushy or sales-focused. This subject line leads with exactly that energy before a single word of the email body is read.
Everything you need to know about email subject lines.
Enter your email subject line in the input field and click “Test subject line.” Our AI instantly analyzes it across 5 key criteria – length, clarity, spam risk, personalization, and engagement – and gives you an overall score out of 100. You also get a detailed breakdown of each criterion with specific feedback, plus 3 improved alternatives you can copy and use right away.
The subject line is the first thing recipients see and the primary factor in whether they open your email. A well-crafted subject line can dramatically improve open rates, while a poor one can send your email straight to trash or spam.
Our AI analyzes your subject line across 5 criteria: length (15%), clarity (20%), spam risk (20%), personalization (20%), and engagement (25%). Each criterion is scored 0–100, and the weighted combination gives you an overall score. A generic subject line typically scores 30–50, while an excellent one scores 75–95.
Keep them between 3–7 words (under 50 characters), use personalization when possible, avoid spam triggers (ALL CAPS, excessive punctuation, words like “free” or “urgent”), and focus on delivering clear value or curiosity. Our tool provides specific feedback and alternatives to help.
Yes, you can test up to 3 subject lines per day without creating an account. With a free Hunter account, you get additional daily tests. Paid plans include the AI Writing Assistant for generating complete cold emails.
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