Email Subject Line Tester
Score your subject line before you send. Length, all-caps, spammy words, and punctuation all influence open rates — the OutSends tester grades your subject line in real time.
How it works
Get started with email subject line tester in a few simple steps.
Type your subject line
The score updates live as you type — no button to click.
Read your score
Get a 0–100 score with clear notes on what to fix.
Improve and resend
Tweak your subject line and watch the score improve in real time.
Why use this free tool
Everything you need, integrated in one workspace.
- Live scoring as you type
- Checks length, all-caps, punctuation, and spam words
- Actionable notes, not just a number
- Free forever, private, runs in your browser
Related tools
More free tools to power your email workflow.
Frequently asked questions
Is the email subject line tester free?
Yes, it is 100% free and works directly in your browser.
What makes a good subject line?
Short subject lines (under 50 characters) with a clear benefit or curiosity gap tend to perform best. Avoid ALL CAPS, excessive punctuation, and spammy words.
Does a high score guarantee opens?
No tool can guarantee open rates, but this score reflects best practices and deliverability red flags that measurably affect them.
Ready to send better emails?
OutSends helps you run cold email campaigns from your own Gmail, SMTP, or API provider — free, no credit card.