Email Subject Line Tester
Score an email subject line on length, spam words and punctuation, and preview how it is truncated in Gmail, Outlook and Apple Mail.
- Characters
- 0
- Words
- 0
- Emoji
- 0
- Spam words
- 0
Checks
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- –
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Spam trigger words found
Inbox previews
- Gmail — iPhone (35 chars)
- Apple Mail — iPhone (40 chars)
- Outlook — desktop (60 chars)
- Gmail — desktop (70 chars)
How it works
Type a subject line and it is scored live out of 100 against the rules that decide whether an email gets opened: length, word count, ALL-CAPS shouting, punctuation spam like !!!, emoji overload and a built-in list of spam trigger words that filters such as Gmail and Outlook weigh heavily. Aim for 20–50 characters and 3–9 words — anything longer is cut off in the inbox.
The inbox previews show exactly where each major client truncates your subject: roughly 35 characters on Gmail for iPhone, 40 on Apple Mail, 60 in the Outlook desktop list and 70 on Gmail desktop. Add your preheader text to see the grey line that appears next to it. Scores are guidance, not a deliverability guarantee — the whole check runs in JavaScript in your browser, so nothing you type is uploaded, logged or sent anywhere.
Frequently asked questions
How long should an email subject line be?
Aim for 20 to 50 characters and 3 to 9 words. Gmail on an iPhone shows roughly 35 characters and Apple Mail about 40, so the first few words have to carry the message. This tester scores anything over 60 characters as too long and previews exactly where each client cuts it off.
Which words trigger spam filters in a subject line?
Phrases promising money or urgency are the usual culprits: free money, act now, cash bonus, risk free, limited time, work from home, guaranteed and similar. ALL-CAPS words and repeated exclamation marks add to the signal. The tester checks your line against a built-in list and names every phrase it finds.
Is my subject line sent anywhere?
No. The tester is pure JavaScript running in your browser, so your subject line and preheader are never uploaded, stored or logged. There is no account, no ads and no server involved — you can even use it with the network disconnected.