Subject line
Nothing here would stop me sending it
What survives the cut
The faded part is what nobody reads. Measured in pixels, because that is what truncates. A character count calls thirty wide letters and fifty narrow ones the same length.
Mechanics
Nothing to fix. 2 checks passed.
- PassYour preview text adds somethingIt carries its own information rather than repeating the subject.
- PassThere is no number in itNot a fault. A number is the cheapest way to be specific. Worth knowing when you have not used one.
Everything here runs in your browser. Your numbers are never sent anywhere, not to me and not to anyone else.
How this is calculated, and what to put in
Why there is no score here
Most subject line tools give you a number out of a hundred. That number is built from other companies’ results.
Your list is not their list. A score tells you nothing you can act on. It also invites you to write for the scorer rather than the reader.
Why this does not mention the obvious metric
You will notice the number everyone optimizes subject lines against is absent. That is deliberate.
Since mail privacy protection, that figure counts images fetched by a server. The person may never have looked. Writing to move it means writing for a machine.
What is left is worth more anyway. Did it arrive, did it get cut off, and did it say something first.
Why this measures pixels
Character counts are the usual advice and they are wrong. Thirty wide letters take more room than fifty narrow ones.
So this measures your own text in a normal inbox font. Three widths, all of which it has to survive. The faded part is what nobody reads.
The preview line is half the space
Every inbox shows a second line next to the subject. Most senders leave it empty or repeat the subject in it.
Left empty, the client takes the first line of your email. That is usually a link telling people to view the message in a browser.