Email Subject Line Tester
Check an email subject line for length on mobile, spam-trigger words, excessive capitals, punctuation and emoji before you hit send.
How to use
- 1Paste your subject line.
- 2Fix any flagged spam words, caps or length problems.
How it's calculated
Checks: under about 50 characters (fits most mobile inboxes), common spam-trigger phrases, share of capital letters, repeated punctuation (!!!) and emoji count.
Frequently asked questions
How long should a subject line be?
About 30–50 characters shows fully on most phones. Put the key words first in case it's cut off.
Do spam words really matter?
Modern filters focus more on sender reputation and engagement, but spammy wording still hurts trust and open rates.
Should I use emoji?
One relevant emoji can help stand out; several can look spammy and may not render in every client.