Free Tools /Marketing
Email Subject Line Tester
Score a subject line on 8 checks and preview it in a desktop and mobile inbox before you hit send.
- Free, no signup
- Runs in your browser
- Nothing stored
Calculating…
Who uses it, and for what
Check a cold email subject before a sequence goes out to 500 people.
Make sure a newsletter subject is not cut off on phones.
Avoid the spam-trigger words that quietly send launch emails to promotions.
How this tool works
8 checks
Length, spam-trigger words, capitals, exclamation marks, emojis, a hook, preview text, and fake Re:/Fwd:.
Inbox preview
See how subject and preview text read side by side, and where a mobile inbox cuts them.
A score to compare versions
Test two or three subjects and keep the strongest.
Frequently asked questions
What is the ideal subject length?
Roughly 20 to 50 characters. Mobile inboxes show around 35 to 45, so put the important words first.
Do spam words really matter?
Less than sender reputation and authentication, but stacked promotional words still push mail toward spam or promotions.
What is preview text?
The line shown after the subject in most inboxes. If you leave it empty, the first words of the email are used.
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Done for you
Want this running inside your business, automatically?
We build the workflow behind tools like this one, wired to your CRM, inbox and apps, and keep it running. Fixed price, from $390 a month.