How should you judge subject length?
Use this checker as a quick formatting pass. Then test subject lines by intent: direct benefit, curiosity, proof, urgency, and objection handling.
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Client-side tool
Email subject line length checker.
Check if your subject line is likely to fit in mobile inboxes and whether it is too vague, too long, or too short.
Subject length
TL;DR
Keep subject lines clear and specific. A shorter line can help mobile visibility, but clarity matters more than hitting a universal character count.
What should a subject line include?
- A specific reason to open.
- A promise the email actually fulfills.
- Language that matches the subscriber's funnel stage.
FAQ: subject line length
What is the ideal email subject line length?
A practical starting range is 35 to 55 characters, but the best length depends on audience, device mix, sender trust, and campaign intent.
Why do subject lines get cut off?
Inbox apps truncate subject lines based on screen size, font, sender name length, and preview text. Shorter subject lines are usually safer on mobile.
Does this checker use AI?
No. It runs in the browser and checks length, word count, and basic truncation risk without AI credits.
Next step
Generate and test funnel subject lines faster.
Use EmailFunnelAI to create subject line variants in context with the rest of the email sequence and funnel goal.
Start free in EmailFunnelAIUse the free tool output as your brief. No credit card required.