Email Subject Line Tester
Test subject lines for character length, spam triggers, and mobile preview truncation.
No spam triggers detected.
No personalization tags. Add {{name}} or [name] for better open rates.
What this tool does
Subject lines determine open rates — too long gets truncated on mobile, spam trigger words hurt deliverability.
Test length, spam warnings, and mobile preview locally before sending campaigns.
How to use it
- 1
Type or paste your email subject line.
- 2
Review character count, spam word warnings, and mobile preview.
- 3
Iterate until length and wording are optimized for inbox display.
Subject line craft
Front-load the value proposition — mobile shows roughly 40 characters. Avoid ALL CAPS and excessive punctuation.
Personalization tokens add length — account for them when checking character count.
Tips
- A/B test two subject lines on 10% of list before full send.
- Avoid spam triggers like "free", "act now", and "guarantee" unless essential.
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Frequently asked questions
Does this send test emails?▼
No. This is a local preview and analysis tool — no emails are sent and nothing is uploaded.
What subject line length works best?▼
Aim for 40–60 characters for mobile visibility. Front-load the most important words.