Paste your subject line
Drop in the subject line you're about to send. Works with cold emails, newsletters, and any outreach.
Used by 6M+ people to get their emails opened
Create, optimize, and use the best email subject line for your campaign.
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A subject line can make or break an email campaign. By adding one or two items of personalization, you can increase your open rates to 40%. Here's how to improve yours.
Drop in the subject line you're about to send. Works with cold emails, newsletters, and any outreach.
See where your subject line stands on length, clarity, spam risk, personalization, and engagement in one score.
Find out exactly which parts of your subject line are costing you opens.
Pick from 3 AI-generated alternatives that address the weaknesses found in your original.
This free subject line analyzer finds and fixes weaknesses in your subject line so that you stand out in the inbox.
Your prospects delete emails without going past the subject line. The ones that demand to be opened are short, specific, and personable to the recipient.
The best subject lines are short, specific, and personable, like these.
Idea for {{company}}'s Q2 pipeline, {{first_name}}
Two personalized attributes, a concrete hook, and 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.
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Generic, impersonal, and sales-first. 65% of decision makers say cold emails fail because they feel exactly this way.
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View all toolsEverything you need to know about getting more opens, from subject lines to send timing.
Read the guideBenchmarks from 31 million emails. See how your subject lines, reply rates, and sequences compare.
See the benchmarksEverything you need to know about testing and improving your email subject lines.
Type or paste your subject line into the input field and click “Test subject line.” The tool scores it out of 100 across five criteria: length, clarity, spam risk, personalization, and engagement. You also get specific feedback on each criterion and 3 improved alternatives you can copy.
Yes. You can test up to 3 subject lines per day without creating an account. A free Hunter account gives you more daily tests. Paid plans add the AI Writing Assistant for generating full outreach emails.
A score of 75 or above means your subject line is well-optimized for opens. Most generic subject lines score between 30 and 50. Aim for 80+ by keeping it 5–6 words, adding personalization, and avoiding spam trigger words.
Subject lines of 5–6 words produce the best reply rates, based on data from 31 million outreach emails. Keep them under 50 characters so they display fully on mobile. Anything shorter than 3 words lacks context, and anything over 9 words gets cut off.
Yes. Subject lines with two custom attributes (like first name and company name) achieve a 40.2% open rate, compared to 35.4% with just one. Using personalization tokens shows the recipient the email was written for them specifically.
Words like “free,” “urgent,” “act now,” and “guaranteed” can trigger spam filters. ALL CAPS and excessive punctuation also hurt sender reputation. The email subject line spam checker flags these automatically so you can fix them before sending.
Not really. “Quick question” subject lines underperform at 28.7% open rate and 2.5% reply rate, compared to 32.9% and 2.9% for other patterns. Overused formulas may feel safe, but recipients and spam filters have seen them too many times.
Keep it 5–6 words. Add at least one personalized attribute. Lead with a specific hook tied to the recipient’s situation, not a generic benefit. Avoid overused templates and run it through a subject line grader before sending.
Yes. The subject line analyzer works for outreach emails, marketing newsletters, transactional emails, and any other email type. The scoring criteria apply universally. For cold email campaigns specifically, you can send tested subject lines directly through Sequences.
Beyond subject lines, verify your recipient list to reduce bounces, personalize your email body with at least 2 custom attributes, and send sequences of 3 emails instead of just one. Campaigns with 3 messages see a 6.8% reply rate compared to 3.3% for single emails.
The AI analyzes your subject line across 5 weighted criteria: length (15%), clarity (20%), spam risk (20%), personalization (20%), and engagement (25%). Each criterion is scored 0–100. The weighted combination gives you an overall score. A generic line typically scores 30–50. An excellent one scores 75–95.
Keep them 5–6 words, personalize with at least one attribute, skip overused patterns like “Quick question,” and avoid spam triggers. Test every subject line with a checker before sending. Data from 31 million emails shows personalized subject lines with 2 attributes reach a 40.2% open rate.
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