0/60
Ideal: 40–60 characters
How to Write Email Subject Lines That Get Opened
Your subject line is responsible for roughly 47% of email opens. Everything else — your content, your offer, your design — only matters if the subject line convinces the reader to click. This tester scores your subject line across seven measurable factors: length, word count, spam word presence, emotional language, urgency, personalization signals, and structural clarity.
The 7 Factors This Tool Scores
- Length (40–60 chars) — The sweet spot visible on all devices. Under 30 chars often lacks context; over 70 chars gets cut off on mobile.
- Spam words — Words like "FREE!!!", "Act Now", "Guaranteed" trigger spam filters and reduce deliverability. This tool flags them instantly.
- Emotional score — Subject lines with emotion (curiosity, urgency, excitement, fear) consistently outperform neutral ones. Numbers and power words boost this score.
- Numbers — "7 ways to…" or "Save $40 today" outperform vague claims. Specificity builds trust.
- Questions — Question-format subjects create an "open loop" that brains want to close. Use sparingly — every third or fourth email.
- Emoji — One well-placed emoji can increase open rates by 25% in the right audience. More than one rarely helps.
- ALL CAPS — Single ALL CAPS words can add emphasis. Multiple ALL CAPS words look like spam and reduce trust.
Subject Line Best Practices by Email Type
- Welcome email — Warm and personal: "Welcome, [Name] — here's what's next" or "You're in. Here's your next step."
- Newsletter — Curiosity or value: "The one productivity mistake everyone makes" or "3 tools I used this week"
- Promotional — Specific offer: "Save 30% today only (ends midnight)" — never vague like "Big sale inside!"
- Re-engagement — Direct and honest: "We miss you — is this still useful?" outperforms aggressive urgency.
- Transactional — Descriptive and clear: "Your order #1234 has shipped" — these get 8× more opens than marketing emails; don't waste the format.