Content
Subject Line Tester
Paste a subject line. We score clarity, length, casing, punctuation, and spam-trigger phrases, then show how it renders across the inboxes that matter.
Want the bigger picture? Read Subject line best practices in the Email Almanac.
How this tool works
Five signals, weighted
- 1
Clarity and impact
Generic openers and filler words drag this down. Numbers and specific nouns lift it. The biggest single lever.
- 2
Content risk
Two phrase lists, high risk and moderate. Hits never block you on their own, but they stack with reputation and authentication signals.
- 3
Length
The sweet spot is 30 to 50 characters. Mobile inboxes cut off at 30 to 40 characters, desktop at 60 to 70. Put the meaningful words first.
- 4
Capitalization
All caps reads as shouting. One word in caps for emphasis is fine. Multiple words start to feel aggressive.
- 5
Punctuation and emoji
Stacked exclamation marks, multiple dollar signs and emoji clusters all add risk. One of each is rarely a problem.
What goes into the score
Length, in characters
When to use it
Reach for it in these moments
Before every send
Run it through before you send. Fixing a subject takes 30 seconds.
When opens drop
If a sequence stops performing, run the recent subjects through one by one. Patterns show up quickly.
A/B test prep
Run both variants. If one scores significantly lower, think twice before shipping that arm against half your list.
Email Almanac
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