Email Subject Line Tester
Analyse your email subject line for length, spam triggers, and effectiveness. Get an instant score with actionable suggestions to improve open rates.
Test your subject line
0 characters
e.g. Your order has shipped! 🚀
💡 Tip: Keep subject lines between 30–50 characters for the best open rates. Most mobile clients truncate after 40 characters.
When to test your subject line
Marketing campaigns
Test subject lines before sending newsletters and promotional emails to maximise open rates.
Transactional emails
Even order confirmations and receipts benefit from clear, non-spammy subject lines.
Cold outreach
First impressions matter - test your sales outreach subject lines to avoid spam folders.
Event invitations
Make sure your event emails get opened by testing for length, clarity, and engagement.
Email subject line best practices
Keep it short and clear
Aim for 30–50 characters. Mobile devices truncate longer subject lines, so front-load the most important words.
Avoid spam triggers
Words like 'FREE', 'ACT NOW', and 'GUARANTEED' increase the chance of landing in spam. Use natural language instead.
Personalise and test
Use the recipient's name or location when possible. A/B test your subject lines to find what resonates with your audience.
Frequently asked questions
A good subject line is 30–50 characters, clearly states the email's value, avoids spam trigger words, and creates enough curiosity to drive an open.
The tester evaluates length, word count, emoji usage, spam word presence, capitalisation, and punctuation. Each factor adds or subtracts from a base score of 70, capped at 0–100.
Words and phrases like 'free', 'act now', 'guaranteed', 'click here', and 'buy now' that email spam filters commonly flag. Using them increases the risk of landing in spam.
In most cases, yes. Emails with emoji in the subject line tend to have higher open rates because they stand out in crowded inboxes. Use them sparingly - one emoji is usually enough.
The preheader is the preview text shown after the subject line in most email clients. It gives recipients extra context and can significantly impact open rates.
Yes, this tool is completely free with no usage limits. Test as many subject lines as you need without creating an account.
The length, emoji, and formatting checks work for any language. However, the spam word detection is currently optimised for English subject lines.
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