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Subject Line Tester

See how your subject and preview text appear in Gmail, Apple Mail, and Outlook - with truncation previews and readability signals.

Your content stays in your browser unless you choose to import into Memo.

Inbox readability

clear

Preview clarity

clear

Subject: 51 chars · 9 words

Preview: 46 chars · Emoji: 0

  • Subject may truncate on mobile

    Your subject is 51 characters; many mobile clients show ~35.

    Try moving the offer closer to the beginning.

Gmail-style (mobile truncation)

M
Memo Studio10:42 AM

Summer collection is here - free s…

Fresh styles and early access for …

Apple Mail-style (desktop)

M
Memo Studio10:42 AM

Summer collection is here - free shipping this week

Fresh styles and early access for subscribers.

Outlook-style (dark inbox)

M
Memo Studio10:42 AM

Summer collection is here - free shipping this week

Fresh styles and early access for subscribers.

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Frequently asked questions

Is this a spam score checker?
No. We show inbox readability and preview clarity signals-not spam scoring.

About this tool

Preview how your subject line and preheader appear in Gmail, Apple Mail, and Outlook-style inbox lists-with truncation previews and readability signals.

How to use Subject Line Tester

  1. Enter sender name, subject line, and preview text.
  2. Compare mobile and desktop truncation.
  3. Review flags and recommendations, then copy or open in Memo.ly.

What it checks or simulates

  • Character and word counts
  • Mobile and desktop truncation
  • All-caps, punctuation, and emoji patterns
  • Generic subjects and preview/subject overlap

Best practices

  • Front-load the most important words in the subject.
  • Use preview text to extend - not repeat - the subject.
  • Keep subjects scannable under ~35 characters on mobile.

Learn more

Disclaimer

Subject Line Tester provides practical guidance and simulation only. Memo.ly does not send email, guarantee inbox placement, certify accessibility or legal compliance, or promise pixel-perfect rendering in every email client.

  • Not a spam score or deliverability test.
  • Inbox rendering varies by client, account, and OS.