Paste your subject line and preview text to get a score, specific fixes and a phone inbox preview. Test three or four versions before you hit send and keep the strongest.
Phone inbox preview
Phones show roughly the first 35 to 45 characters of a subject. Spam filters judge your sending reputation far more than single words, so use the word warnings as a nudge, not a rule.
What the tester checks
The score is built from the things that most often hold a subject line back:
- Length. Phones show roughly the first 35 to 45 characters. Longer lines aren’t banned, but the key words need to be at the front.
- Capitals and punctuation. ALL CAPS and “!!!” read as shouting to people and to filters.
- Spam-prone words. Phrases like “100% free”, “act now” or “you won” are common in junk mail. One won’t sink a trusted sender, but stacking them is risky.
- Fake replies. Starting with “Re:” or “Fwd:” on a new email gets opens once and costs you trust after.
- Preview text. If you leave it empty, inboxes show the first words of your email, which is often “View this email in your browser”.
- Sender name. People decide whether to open based on who sent it as much as on the subject.
A quick way to write better subject lines
Write down what the reader gets from the email in plain words, then cut it to fit. “Our November newsletter” tells nobody anything. “5 fixes to make before Black Friday” tells them what’s inside and why now. Specific numbers, a clear benefit and a little curiosity go a long way.
Then use the preview text as a second line, not a repeat. If the subject makes the promise, the preheader can add the detail that tips someone into opening: “Number 3 takes ten minutes.”
Don’t forget deliverability
The best subject line does nothing if the email lands in spam. Gmail and Yahoo now expect bulk senders to have SPF, DKIM and DMARC set up and to offer one-click unsubscribe. Use our SPF and DMARC generator to build the records, and read our guide to subject lines and preview text that get opens for more examples.
Common questions
What is a good open rate?
It varies by industry and list, and Apple Mail Privacy Protection inflates opens. Compare your emails against each other over time rather than against an industry average, and watch clicks as well as opens.
Do emojis in subject lines help?
Sometimes. One relevant emoji can help a line stand out in a busy inbox. Several look cluttered, and older email apps may show them as empty boxes, so test with your own list.
Are spam trigger words still a thing?
Much less than they used to be. Modern filters care most about your sending reputation, authentication and whether people open or delete your emails. Spammy wording can still nudge a borderline email the wrong way.
Is my subject line stored anywhere?
No. The tester runs entirely in your browser and nothing you type is sent to our server.