Email Subject Line Tester
Check your subject line’s length, spam trigger words, caps, and emoji use with instant feedback to lift open rates.
The line that decides your open rate
Everything in an email campaign hinges on whether the subject line earns the open. Too long and it's truncated on mobile before the hook lands; loaded with spam-trigger words or shouting caps and it risks the promotions tab or the junk folder. This tester scores the essentials at a glance — character count, word count, emoji use, and a scan for common spam-filter phrases — and lists specific warnings you can act on.
Aim for a punchy 30–50 characters, lead with the value or curiosity, keep it to one emoji at most, and rephrase anything the tester flags as spammy. Small tweaks here compound across every send.
Private and instant
Your subject lines never leave your browser.
Frequently Asked Questions
How long should an email subject line be?
Aim for about 30–50 characters. Mobile inboxes show roughly 30–40 characters before truncating, so front-load the hook. This tester flags subjects that run too long.
What are spam trigger words?
Words and phrases like “free”, “guarantee”, “act now”, and excessive punctuation or ALL CAPS can raise spam-filter suspicion. The tester highlights common triggers so you can rephrase.
Do emojis help subject lines?
A single, relevant emoji can lift open rates, but overuse looks spammy. The tester counts emojis so you can keep it to one or none.
Is this tool free and private?
Yes. The analysis runs in your browser — nothing is uploaded or stored.
Count and check any text as you write, on any site.