Start with the actual subject
Paste the subject your recipient will see. Resolve variables for an accurate length check or use the flags to spot unfinished personalization.
Free subject line testerMake the first line
Make the first line
worth a second look.
Test and compare email subject lines for free with explained editorial checks, character counts, and illustrative inbox previews. No sign-up or content upload.
A clearer first impression.
Review length, placeholders, formatting, pressure language, and thread context. Add a second subject to compare the same checks side by side.
Test the wording. Understand the score.
Compare the same checks
Add a second line to compare length, formatting, pressure language, and conversation context under identical rules.
Review the whole email
Use the inbox preview as an illustration, then check that the subject accurately describes the body. Real audience testing answers questions this editorial score cannot.
Is the subject line tester free?
Yes. It runs locally, without an account, payment, or content upload.
Does the score predict open rates?
No. It is the sum of the six displayed editorial checks. The points and reasons are visible for each check. It is not a deliverability test or an estimate of audience response.
Is the inbox preview exact?
No. It illustrates truncation at two widths. Email apps, device sizes, fonts, sender names, and privacy settings affect the actual display.
Bring your own context.
Tell us what you are working on. Let’s find a useful next step.