Free tool
Email Subject Line Tester
See how your subject line and preview text look in an inbox, and what might get them cut off or flagged.
Free, no signup. Everything runs in your browser; what you type is never sent to us.
Your email
People see this before the subject. A real name or a brand they know usually beats a no-reply address.
53 characters · 10 words
68 characters
Compare other subject lines
Up to 8. Handy for choosing between two or three ideas before you send.
How it looks in an inbox
Desktop inbox
Android-style phone
The Sunday drop: 12 new arrivals and 3 rare pressings
Plus a listening night this Friday. Doors at 7, 40 seats, no phones.
iPhone-style mail
The Sunday drop: 12 new arrivals and 3 rare pressings
Plus a listening night this Friday. Doors at 7, 40 seats, no phones.
Approximate. Real widths depend on the device, app, font size and settings, so treat this as a guide rather than a guarantee.
Checks
- Note
53 characters
Fine on desktop, but phones often cut a subject off at around 35 to 45 characters, so put the important words first.
- Good
68 characters
A good length: enough to add to the subject, short enough to mostly show.
These are guidelines. Whether an email reaches the inbox depends mostly on your sender reputation and email authentication, not on any single word.
Comparison
| Subject line | Chars | To check | |
|---|---|---|---|
| New arrivals are in | 19 | Nothing flagged | |
| This Sunday: 12 new records, 3 you will not see again | 53 | Nothing flagged | |
| Your first pick of Sunday’s arrivals | 36 | Nothing flagged |
What this checks
It shows your subject line and preview text the way a few common inboxes lay them out, and flags the things that tend to cause trouble: a subject that gets cut off before the point, shouting capitals, heavy punctuation, a preview that repeats the subject, an empty preview, and sales-sounding phrases.
Paste a few alternatives underneath and compare them side by side. It is quicker than guessing, and it costs nothing to try five.
What it cannot tell you
No tool can promise your email lands in the inbox or gets opened. That depends mostly on your sender reputation, whether your domain is authenticated, and whether people who know you want to hear from you. Our posts on spam trigger words and SPF, DKIM and DMARC explain what actually moves the needle.
Use this as a proofreader, not a judge. The only real test of a subject line is how your own list responds to it.
Questions
- How long should an email subject line be?
- There is no magic number. Many phones show roughly 35 to 45 characters and desktop inboxes about 60 to 70, so the first few words should carry the meaning. A longer subject is fine if the start works on its own.
- Do spam trigger words really send email to the spam folder?
- Rarely, on their own. Modern filters look mainly at who is sending, whether the domain is authenticated, and how recipients react. Words like "free" or "limited time" can still make a message read as pushy, which is why the tool mentions them, but it will not claim they decide anything.
- What is preview text?
- The line of grey text after the subject in the inbox list, also called a preheader. If you do not set one, the inbox shows the first text from the email body, often "View in browser". A short, specific line is a free second subject line.
- Should I use emojis in subject lines?
- Sometimes. One can make a subject stand out; several look like marketing noise, and they render a little differently in each app. Test it on your own list, and check the result on a phone first.
- Is what I type sent anywhere?
- No. The checks run in your browser. Nothing you type here is uploaded or stored.
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Worth reading next
- Email Subject Line Length: How Many Characters Show
- Email Preview Text: Character Limits and How to Set It
- Subject Line "Hacks" That Work vs. the Ones That Don't (Mythbusting)
- "Spam Trigger Words": Why the Avoid-These-Words Advice Is Mostly Outdated
- The "From" Name: Why Who It's From Matters More Than the Subject Line