Email subject line tester
Test a subject line before you send: its length, how it looks in a phone and a desktop inbox, words that often appear in spam, capitals, punctuation and emoji. Add your preview text to see the whole line readers get.
How to use the Email Subject Line Tester
- 1Type your subject line and, if you have one, the preview text (preheader).
- 2Read the checks: green is fine, amber is worth a look and red needs fixing.
- 3Look at the phone preview to see where the subject is likely to be cut.
- 4Adjust it until the key words are in the first 35 to 40 characters.
Frequently asked questions
How long should an email subject line be?
Around 30–50 characters is a safe range. Phones show roughly the first 35–40 characters, so put the most important words first and use the preview text for the rest.
Do spam trigger words send my email to spam?
Rarely on their own. Gmail, Outlook and others mostly judge your sender reputation, authentication (SPF, DKIM, DMARC) and how readers react. Several trigger phrases plus capitals and "!!!" do add up, so the tester flags them.
What is preheader text?
The short line most inboxes show after or under the subject. If you don't set one, the inbox shows the first text of your email, which is often "View in browser".
Are emoji in subject lines a good idea?
One relevant emoji can help a subject stand out, but it can look unprofessional for some brands and shows as a box in a few older apps. Never rely on an emoji to carry the meaning.
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