Email subject line tester
Sign up free

Brevo ecommerce free tools

Email subject line tester

Score your subject line before you send. The tester checks length, spam triggers, capitalization, emoji and punctuation, then shows exactly where your subject and preview text truncate in Gmail, Outlook and Apple Mail.

Scores update as you type. Want variants? Generate options with Brevo's free AI email generator.

0 to 100 score with reasonsLive inbox previewsSpam trigger detectionFree and unlimited, no signup

What the score is built on

Length that survives the inbox. Around 30 to 50 characters keeps the whole thought visible on desktop and most of it on mobile, where the majority of ecommerce opens happen. The preview text is your second subject line: use it, or the client fills it with whatever your email starts with.

Spam triggers are about accumulation. One "free" will not filter you. FREE!!! in caps with three exclamation marks alongside "act now" and "no risk" starts to look like every message Gmail has ever binned. The tester flags trigger words by category so you can trade them deliberately.

Casing and punctuation set the register. ALL CAPS words, stacked punctuation and more than a couple of emoji read as shouting to both filters and humans. Sentence case with one point of emphasis consistently outperforms.

Test, then A/B test. A score catches mechanical problems before you send. Which of two good subject lines wins is an empirical question: run them against each other on a slice of your list and let the winner send to the rest.

Great subject lines deserve real A/B tests

The tester catches mechanical problems. Brevo finds the winner: split test subject lines on a slice of your list and auto-send the better one to everyone else.

  • Built-in A/B testing on campaigns
  • Free AI subject line and email generator
  • Send-time optimization per contact
  • Free plan with 300 emails a day, no card required
Create your free accountTry the AI email generator
500k+businesses send with Brevo worldwide
300free emails a day on the free plan
All-in-oneemail, SMS, WhatsApp, push and automation
EUhosted and GDPR compliant by design

More free tools for ecommerce marketers

Part of Brevo's free marketing tools. Free to use, built for merchants and the agencies that serve them.

Abandoned cart revenue calculator

See how much revenue a 3-email plus SMS plus push recovery flow would win back for your store.

Use this toolSMS and WhatsApp cost calculator

Estimate per-country campaign costs across SMS and WhatsApp, with a live segment counter.

Use this toolEmail list health checker

Audit your list for invalid, disposable and role-based addresses. Your list never leaves your browser.

Use this toolEcommerce email program grader

Grade your store's email program across capture, welcome, cart recovery and deliverability.

Use this toolPeak season campaign calendar

Generate a dated BFCM send plan with channels, segments and offers for October to December.

Use this tool

Frequently asked questions

What is the ideal email subject line length?
Roughly 30 to 50 characters. Gmail desktop shows about 70 characters of subject; phones show 33 to 41. Put the payoff in the first 30 characters so it survives every client.
Which words trigger spam filters?
Filters weigh accumulation, not single words. Risky categories include money claims (free, cash, save big), urgency pressure (act now, last chance), and shouting (all caps, repeated punctuation). Modern filters also weigh your authentication and engagement, which matter more than any single word.
What is preview text and why does it matter?
The line of gray text after your subject in the inbox. If you do not set it, the email client pulls the first text it finds in your email, often 'View in browser'. Treat it as a second subject line that finishes the thought.
Do emoji hurt open rates?
Not inherently. One relevant emoji can lift visibility; three start to look like spam and can break rendering in older Outlook. The tester flags counts above two.
Is this tester free?
Yes, completely, with no usage limit and no signup. It runs entirely in your browser.