Is The Score A Deliverability Guarantee?

No. The checks are editorial guidance based on widely observed inbox behavior. Deliverability also depends on sender reputation, authentication and list quality, which no subject line tool can see.

Where Does The Spam Phrase List Come From?

It is a curated list of phrases long associated with junk filtering — urgency clichés, money claims and pressure language. One match is a caution; several together are the real problem.

How Long Should A Subject Line Be?

30 to 50 characters keeps the whole promise visible in most clients; many phones truncate around 41. The preview shows the truncation instead of making you guess.

Is My Subject Line Uploaded Anywhere?

No. Analysis and previews run entirely in your browser.

Email Subject Line Tester

Score an email subject line, preview it in a desktop and phone inbox, and catch spam-filter phrases before you hit send.

Subject Line

Rule-based checks run locally as you type — nothing is sent anywhere.

Subject35 Characters · 8 WordsFrom Name

Preview Text

Desktop Inbox

FFox StudioYour March report: 3 wins and 1 fix — Plus the one metric we would watch closely next month.9:41 AM

Phone Inbox

Fox Studio9:41 AM

Your March report: 3 wins and 1 fix

Plus the one metric we would watch closely next month.

Guidance is editorial and rule-based — deliverability also depends on sender reputation, list quality and content. Phones truncate near 41 characters; desktop clients show more.

Subject Score

Strong

Rule-based editorial score out of 100

Length35 characters — 30 to 50 survives most inboxes; phones cut off near 41.
Word Count8 words — 4 to 9 keeps the promise scannable.
Spam TriggersNo common spam-filter phrases detected.
All-Caps WordsNo shouting — good.
Exclamation MarksNo exclamation marks.
EmojiNo emoji — fine; one relevant emoji can help.
PersonalizationNo merge tag — a first-name token often lifts opens.
SpecificityA number makes the promise concrete.

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What Is the Email Subject Line Tester?

The Email Subject Line Tester scores a subject line with transparent, rule-based checks: length against inbox cutoffs, word count, common spam-filter phrases, all-caps words, exclamation marks, emoji count, merge-tag personalization and specificity. A live inbox preview shows exactly how the subject and preview text sit together on desktop and where a phone truncates the line. Everything runs locally as you type.

How It Works

Type the subject and optional preview text. The desktop and phone inbox mockups update live — phones cut off near 41 characters — and the score panel lists every check with what to fix. Flagged spam phrases appear as chips so you can reword them.

When to Use It

Use it while drafting newsletters, product announcements and outreach, before the send button makes the decision permanent.

Frequently Asked Questions

Is The Score A Deliverability Guarantee?: No. The checks are editorial guidance based on widely observed inbox behavior. Deliverability also depends on sender reputation, authentication and list quality, which no subject line tool can see.
Where Does The Spam Phrase List Come From?: It is a curated list of phrases long associated with junk filtering — urgency clichés, money claims and pressure language. One match is a caution; several together are the real problem.
How Long Should A Subject Line Be?: 30 to 50 characters keeps the whole promise visible in most clients; many phones truncate around 41. The preview shows the truncation instead of making you guess.
Is My Subject Line Uploaded Anywhere?: No. Analysis and previews run entirely in your browser.

Found an issue? Send Feedback. See our data sources and update policy for tools that depend on changing information.