Free tool · Deliverability
Email Subject Line Tester
Paste a subject line to get an instant deliverability score for length, spam-trigger words, ALL-CAPS, punctuation and emoji — plus the urgency cues that lift opens — and see exactly how it will look in a real desktop and mobile inbox.
Your subject line
Scored entirely in your browser against a heuristic checklist — length, spam-trigger words, ALL-CAPS, punctuation, emoji and urgency. Nothing is sent anywhere. Use it to shortlist, then A/B test the winners.
Deliverability score
Breakdown
Length
No spam-trigger words
Urgency detected
Inbox preview
Desktop
Mobile
Both rows truncate exactly like a real client — the narrower a screen, the sooner your subject and preheader get cut off. Front-load the words that matter.
Two ways to keep urgency out of the spam folder
1. Show the deadline, don't shout it.The safest way to create urgency is a real, visual countdown in the email body — not risky words like “ACT NOW” or “FREE” in the subject. A live Tickvio countdown timer does the persuading, so your subject line can stay clean and score higher.
2. Only send to addresses that exist. Even a perfect subject line lands in spam if your list is full of dead or risky addresses. Verify and clean your list with Qualisend before the next send to protect your sender reputation.
Questions
What makes a subject line score well?＋
The tester rewards a length in the 30–50 character sweet spot (so it doesn't truncate on mobile), no common spam-trigger words, restrained punctuation and emoji, and one or two genuine urgency cues rather than a wall of hype. Everything runs as a heuristic in your browser — treat the score as a directional guide, then A/B test the winners with your real audience.
Why does the tester like urgency but warn about spam words at the same time?＋
Urgency is one of the most reliable ways to lift opens and clicks — but the moment you spell it out with phrases like 'ACT NOW' or 'FREE $$$', filters get suspicious. The safest way to create urgency is to show a real deadline instead of shouting about it: a live countdown timer in the email body does the persuading without loading the subject line with risky words.
Is this tool free, and does anything get sent to a server?＋
It's completely free with no signup, and nothing leaves your browser — the subject line, preheader and score are all computed on-device. If you want to actually build the urgency you're scoring for, Tickvio's countdown timers also have a free plan.
Keep going
Related guides & tools
Countdown timers & deliverability
Create urgency without tripping filters
How to improve email deliverability
The fundamentals that keep you in the inbox
Urgency & FOMO line generator
Write subject lines that score higher
Flash sale timers
The highest-urgency use case
Free email countdown timer
Show the deadline instead of shouting it
Now make the urgency actually tick.
Tickvio adds a live countdown timer to any email or web page — it renders in real time for every viewer, in every inbox. No code, works with 50+ ESPs. Free plan included.