IGSendMail

Email Subject Line Tester

This free email subject line tester scores your subject line from 0 to 100 as you type, checking length, word count, spam-trigger words, ALL-CAPS, punctuation, emojis, personalization, and power words — then shows a live inbox preview of how it renders on mobile and desktop. No signup, fully private in your browser.

0 chars 0 words

Try an example:

Inbox preview

Mobile inbox (~38 chars)
Y
Your Brand9:41 AM
Your subject line will appear here
Preheader / preview text shows here after the subjec…
Desktop inbox (~60 chars)
Y
Your Brand9:41 AM
Your subject line will appear here
Preheader / preview text shows here after the subject.

Truncation points are approximate — exact cut-offs vary by client and screen width.

0/100
Weak

Type a subject line to see your score.

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How the subject line analyzer scores your line

This subject line checker runs eight deterministic heuristics entirely in your browser and combines them into a single 0–100 score. Nothing is uploaded — the same input always produces the same result, so you can A/B your wording with confidence.

Length

Rewards 28–50 characters; penalizes over 60 (mobile truncation) and under 15 (too vague).

Word count

Rewards a scannable 3–9 words and nudges down very short or wordy lines.

Spam triggers

Scans against ~60 known spam phrases and flags each one it finds.

Caps & punctuation

Penalizes ALL-CAPS words and excessive !!! or multiple ? marks.

Emoji balance

Mild positive for one emoji; penalizes three or more.

Personalization

Detects merge tags like {name}, {{first_name}}, %FNAME%, *|FNAME|*.

Power words

Rewards emotional and curiosity drivers from a 40+ word list.

Numbers & curiosity

Small boost for a digit and for a question that sparks curiosity.

Why subject lines matter

The subject line is the single highest-leverage piece of copy in any email. It is the only thing — alongside the from name and preview text — that the recipient sees before deciding to open, archive, or report. A subject line that is too long gets cut off on mobile, where the majority of email is now read; one stuffed with spam-trigger words and ALL-CAPS can be filtered out before a human ever sees it. Even a few points of open-rate improvement compounds across every downstream metric: clicks, conversions, and revenue.

That said, no subject line can rescue a poor sending reputation. Mailbox providers weigh authentication, engagement history, and list hygiene far more heavily than wording. Use this tester to sharpen the words, and let IGSendMail's deliverability stack handle the reputation side so your well-crafted line actually lands in the inbox. For a full domain check, run our free deliverability audit.

Frequently asked questions

Aim for roughly 28 to 50 characters, or about 3 to 9 words. Mobile email apps typically truncate subject lines around 33 to 41 characters, so put the most important words first. Subject lines over 60 characters almost always get cut off on phones, and very short ones under 15 characters often look vague or spammy.

A single, relevant emoji is generally fine and can lift open rates by adding visual contrast in a crowded inbox. The risk comes from overuse — three or more emojis, or emojis used in place of words, can read as spammy and may render inconsistently across email clients. This tester gives a mild positive for one emoji and penalizes more than two.

Classic spam-trigger phrases include 'free', 'act now', 'guarantee', 'risk-free', 'limited time', 'click here', '100% free', 'winner', 'cash', 'buy now', and symbols like '$$$' or '!!!'. No single word guarantees the spam folder, but stacking several of them — especially alongside ALL-CAPS words and heavy punctuation — raises your spam score. The tester flags each trigger word it finds.

No. Subject line quality is one signal among many. Inbox placement is driven mostly by sender reputation, authentication (SPF, DKIM, DMARC), list hygiene, engagement history, and content. A strong subject line improves open rates and avoids obvious spam triggers, but it cannot override a poor sending reputation. IGSendMail handles authentication and reputation automatically.

Yes, when you have reliable data. Tokens like {name}, {{first_name}}, or %FNAME% let you insert a recipient's name or attribute, which typically improves open rates. The key is a clean fallback — if the field is empty the email shouldn't read 'Hi {name},'. The tester detects common token formats and rewards their presence.

Write subject lines that land in the inbox

Score your wording here, then send it through IGSendMail — automatic SPF/DKIM/DMARC, an AI subject line generator, and 99% inbox delivery, all on the free plan.

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