Subject Line Checker
Subject Line Checker is a free tool that scores your email subject line for length, advert-like words, shouting and emoji, and shows how it looks on a phone.
- Free
- No sign-up
- Runs in your browser
Score an email subject line before you send it, and see how it will look in a phone inbox — which is where most email is opened, and where about 35 characters is all you get. We check length, advert-flavoured words, shouting, emoji and personalisation.
Your workspace
Fill in the details above, then press the button to see your result.
Guide
How to use it
- 1Type or paste your subject line.
- 2Look at the phone preview first. If the point is not in the first 35 characters, rewrite it.
- 3Check the warnings. One or two are usually fine; five means the line reads like an advert.
- 4Fix the technical side separately with our Email Safety Checker — that is what actually affects delivery.
Common questions
Will avoiding these words keep me out of spam?
Largely no, and any tool that says otherwise is selling a superstition. Modern filters weigh your domain's authentication, sending reputation and how people engage with your mail. Word lists are about whether a human opens it, not whether it arrives.
How long should a subject line be?
Short enough that the point survives a phone, which means about 35 characters for the important part. The full line can be longer; just do not put the payload at the end.
Do emoji help or hurt?
One, used deliberately, can lift open rates. Three or more reads as a discount blast. It also depends entirely on your audience — test rather than assume.