Email subject line tester

Paste your subject line and see how it lands — mobile and desktop preview, spam-word flags, and an open-rate likelihood score with tips. Everything runs in your browser; nothing is uploaded.

Your subject line0
Preheader / preview text (optional)
Type a subject line above to see how it looks in the inbox.

Everything runs in your browser. No sign-up, nothing uploaded.

How it works

STEP 1

Paste your subject line

Drop in the subject you plan to send. Add the preheader too for a truer inbox preview.

STEP 2

Read the checks

See the mobile and desktop preview, the length, any spam-trigger words, and an open-rate likelihood score.

STEP 3

Apply the tips & retest

Follow the suggestions, tweak your line, and test again until the score is green. Copy the report when you are done.