For marketers · Subject lines
Email subject line testing before you send
Subject line testing with an email subject line tester lets you hear why a reader would choose one line over another before you send. Show two or three candidates to verified UK adults. We aim for first answers within about 15 minutes in UK daytime, though replies may take longer for now.
We review requests by hand.
Questions for subject line testing
Choose the decision first. Do you need to make the topic clearer, or does the line sound pushy?
- Example: Which PostPatch email would you open: ‘Latest news’ or ‘Your garden plan’?
- What would you expect this email to contain?
- How helpful does this subject line feel, from 1 to 5?
Text options can each be up to 80 characters. To test the subject and preview text together, put them into one screenshot and ask for a first impression.
What an email subject line tester tells you
Illustrative PostPatch example: ‘Your garden plan’ gets 14 of 20 votes; ‘Latest news’ gets six. People say the first line tells them what they will receive, while the second could be about anything. That is a reason to send the specific candidate into a real email test. These are stated choices from a mixed pool, not measured opens from your list.
How to run a subject line test
- Write two or three lines with the same sender and offer in mind. Avoid changing the message behind the line at the same time.
- Ask 5 to 50 UK adults which they would open. They answer blind, without seeing your name or anyone else's vote.
- Read the split and their one-line reasons. Keep the useful wording; then judge actual performance in your email platform.
Browse other quick questions if you also need to check the body copy or landing page.
Why ask readers before sending?
You may know that ‘Latest news’ contains useful advice. A stranger sees only two vague words in the inbox. Outside readers can point to the missing context before the message goes to your list. Every answer carries a signed receipt listing its checks. See what those checks cover.
Honest limit: A quick choice does not predict open rate. Participants are mixed UK adults, not your subscribers, and they do not see the rest of a real inbox. This test does not check deliverability or spam filtering. Use it to improve a candidate, then rely on your own email results.
What subject line testing costs
Asking is free during early access. At paid launch, a quick take starts from 30p an answer plus 50p a question (launch example). Twenty quick takes would be about £6.50. You see the quote first.
Your questions, answered
How do I test email subject lines?
Show two or three subject lines and ask which one readers would open, then inspect the reasons. Keep the sender and underlying offer the same so you know what they are comparing. After revising, a live split test in your email platform tells you what your own subscribers actually do.
Is there a free email subject line tester?
Asking here is free during early access, by invitation. You can test a pick-one choice with verified UK adults and read why they chose it. The paid-launch example has a per-answer charge plus a question fee, shown in a quote before posting.
How long should a subject line be?
Write the shortest line that makes the email's subject clear without hiding a useful detail. Display space varies by inbox and device, so look at a mobile preview rather than relying on one fixed character count. The text options here can each hold up to 80 characters.
Can I test preview text too?
Yes, as part of one image showing the subject and preview text together. A person can then tell you what the pair suggests. Text-only options are simpler for choosing between subjects; a screenshot is better when the sender, preview and line work as a unit.
Does subject line testing predict open rates?
No. It gives stated preferences and reasons from a small group that may not match your list. PostPatch's illustrative 14-to-six result favours a clearer line, but it is not an open-rate forecast. Use your own send or email-platform experiment for observed opens.
What does subject line testing cost?
It is free to ask during early access. At paid launch, a quick take starts from 30p an answer plus 50p a question (launch example); 20 quick takes would cost about £6.50. The actual price appears in the quote before posting.
Find out what people really think.
Free during early access. No card needed.
Free during early access. We review requests by hand. Have an invite code? Join