Subject Line Analyst
Analyze your subject lines.
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Quick Tip
Type or paste the subject line you are considering.
About This Tool
Why use Subject Line Analyst?
Score a subject line before you send it. The checks are the ones that measurably affect open rates: character length against the mobile truncation point, word count, whether an emoji is present, and whether the line is in all capitals — which costs heavily, because it reads as shouting to both recipients and filters.
Length is the check that matters most. Gmail on a phone shows roughly 30 to 40 characters and Apple Mail around 40, so a subject line running past 60 is being cut off for the majority of your audience — mobile is where over half of all email is opened. The tool treats 30 to 60 characters as the target band and counts your words against a limit of ten, because the front of the line is the part that is always read.
Key Benefits
Length against mobile truncation
Scored against the 30 to 60 character band, because phones cut subject lines well before desktop clients do.
All caps penalised
A subject line in capitals takes the heaviest penalty here, as it does with recipients and filters alike.
Live as you type
The score and the counts update with every keystroke, so you can iterate on the wording immediately.
How to use Subject Line Analyst
- 1
Type or paste the subject line you are considering.
- 2
Watch the score and the character count update as you type.
- 3
Read the flags — length, capitalisation, emoji and word choice.
- 4
Rewrite so the most important words come first, in case the line is truncated.
Best use cases
Check a subject line before a campaign send.
Compare two options and pick the stronger one.
Make sure a line is not truncated on mobile.
Sanity-check a cold outreach subject before a sequence starts.
Subject Line Analyst FAQs
What subject line length should I aim for?
30 to 60 characters. Gmail on a phone shows roughly 30 to 40 and Apple Mail around 40, and over half of email is opened on a phone, so put the important words at the front.
Do emojis help?
One relevant emoji can lift open rates in consumer email. Several, or any at all in formal B2B, tend to backfire. Treat it as a tool for a particular audience, not a default.
Why is all caps penalised so heavily?
It reads as shouting, it is strongly associated with spam by recipients, and it is a well-established filter signal. There is no context in which it helps.
Does a high score guarantee a good open rate?
No. The score measures mechanics — length, capitalisation, word choice. Relevance to the specific recipient and your sender reputation matter more, and neither can be measured from the line alone.
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