Email subject line tester
See your subject the way the recipient will: cut off on a phone, next to thirty other emails.
Inbox preview
Better subject lines
AI · on requestPaste text above first.
AI can make mistakes. Check names, numbers and commitments before you send.
Subject line patterns that work at work
| Purpose | Pattern | Example |
|---|---|---|
| Need a decision | Topic: decision + deadline | Office move: pick a date by Wed |
| Need a review | Review: document (time needed) | Review: Q3 deck (10 min) |
| Sharing information | FYI: topic, key fact | FYI: Portal down Sat 2–4 am |
| Following up | Topic: the next step | Acme contract: next step is legal |
| Introduction | Intro: A ↔ B (reason) | Intro: Maya ↔ Tom (pricing data) |
Questions people ask
How long should an email subject line be?
Keep it under about 50 characters so it isn’t cut off on phones; many mobile mail apps show roughly 30–45 characters in the inbox list, and desktop clients around 60–70. Put the most important words first so a truncated subject still makes sense.
What makes a good business email subject line?
It is specific (names the project or topic), says what you need (review, approve, decide, FYI) and includes a deadline if there is one. “Q3 vendor report: sign-off needed by Fri” lets the reader triage without opening the email.
Which words trigger spam filters?
Modern filters weigh sender reputation and authentication far more than individual words, but promotional phrases like “free”, “act now”, “100% guaranteed” or “limited time”, ALL-CAPS and stacked exclamation marks still look like marketing to both filters and people. In a work email, they cost trust.
How does this subject line tester score my subject?
It runs seven checks in your browser: length, word count, spam-style words, ALL-CAPS, exclamation marks, generic wording and whether an action or deadline is stated. The score is the share of checks passed. The AI option suggests five alternatives, using your email body for context if you add it.