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Newsletter subject line scorer
Paste a subject line and preheader and check them against six plain rules: length, clarity, specificity, punctuation and caps, preheader, and promise.
What this tool tells you and when to use it
The subject line scorer checks a newsletter subject line and its preheader against six plain rules. It tells you whether the line is short enough to survive a phone inbox, whether it names the content or just the container, whether it carries anything specific, whether the punctuation or capitals read as spam, and whether the preheader is set and short enough. The sixth rule, that the promise matches the content, is one a tool cannot score; the page asks you to answer it.
It does not predict an open rate and it does not use a banned-word list. Mailbox providers do not publish one. The rules below are the whole scoring logic, with the vendor guidance each one leans on. Everything else is Sawa's working rule, stated as such.
- Length. Pass at 60 characters or fewer and 9 words or fewer, which is Mailchimp's recommendation. Up to 80 characters is a warning. Longer fails.
- Clarity. A warning if the line leans on a container word such as "newsletter", "update", "issue" or "exciting" instead of naming what is inside. Sawa's rule.
- Specificity. Pass if the line carries a number, a name, or a concrete question. Sawa's rule.
- Punctuation and caps. Fail at more than 3 punctuation marks, which is Mailchimp's guidance on the same page, or at fake replies, stacked marks and urgency phrases. A word in capitals is a warning: there is no published rule against it, it just reads as shouting.
- Preheader. Pass at 90 characters or fewer, which is Litmus's recommendation. A warning if it is empty, because the inbox then pulls the first text it finds, often a "View in browser" link, as Mailchimp's preview text page explains.
- Promise matches the content. Not scorable. Read the first paragraph of the issue and decide.
Use it when you are choosing between two lines, or when an issue underperformed and you want a reason that is not "the algorithm". The guide behind this tool, how to write a newsletter subject line that gets opened, has ten before-and-after rewrites.
Use the tool
- You decideLengthType a subject line to score it.
- You decideClarityDoes it name the content, not the container?
- You decideSpecificityDoes it include a number, a name, or a concrete question?
- You decidePunctuation and capsNo more than 3 punctuation marks; no shouting.
- CheckPreheaderNo preheader. If you leave it blank, the inbox pulls the first text it finds, often a "View in browser" link.
- You decidePromise matches the contentNot scorable by a tool. Read the first paragraph of the issue: does it deliver what the subject line names? If not, change the subject line, not the paragraph.
Where this comes from
This tool was built for the guide How do you write a newsletter subject line that gets opened?, which explains the reasoning behind each option and what to check after you start. It suggests a starting point from a simple planning rule, not from measured results.