Type a subject line and see its length against real truncation numbers, matches against 187 terms copied verbatim from published deliverability guidance, and the mechanical counts (capitals, exclamation marks, emoji, merge tags). Every check and every term is on this page.
Length, guidance-term matches, capitals, punctuation, emoji and merge tags appear here as you type.
Your subject line never leaves this page. The checks run entirely in your browser: no upload, no server, no storage.
This tool checks structure: length, matches against published word lists, and mechanical counts. It cannot measure emotional impact, predict open rates, or tell you where any one email will be filed. A subject line that passes every check here can still be ignored, and one that trips several can still perform. No tool can promise otherwise.
The term matches deserve a specific caveat. Inbox providers do not publish their filter rules, and modern filtering weighs sender reputation and engagement far more than any single word. So a match is reported as exactly what it is: a term flagged in published deliverability guidance, with the source named and dated. The tool never claims a delivery outcome.
| Check | What it does |
|---|---|
| Length | Character count, with a truncation note: mobile inboxes cut off around 30 to 43 characters and desktop around 60. Basis: AWeber, "How Long Should an Email Subject Line Be?" (fetched 2026-07-14): the average mobile inbox shows about 30 characters, most mobile clients stop between 33 and 43, and desktop shows about 60. |
| Deliverability-guidance terms | Matches against 187 terms copied verbatim from published deliverability guidance (every term sourced and dated in spamTriggers.SOURCES.md). A match is information, not a verdict: no tool can know where any one email will be filed. |
| All-capitals check | Flags a subject whose letters are entirely capitals. Basis: Mailchimp, "Most Common Spam Filter Triggers" (fetched 2026-07-14) lists "Subject is all capitals" among the most common triggers it observed. |
| Exclamation marks | Counted and reported. No judgement attached; you decide. |
| Emoji | Counted and reported. No judgement attached; you decide. |
| Personalisation tokens | Detects {{name}}, *|FNAME|*, %%name%% and {name} style merge tags, and reminds you to set fallback text so a missing field never renders the raw tag. |
Sources for the constants: length numbers fromAWeber's subject-line guidance(fetched 2026-07-14); the all-capitals trigger fromMailchimp's published trigger list(fetched 2026-07-14).
All 187 terms were copied verbatim from the named source on the fetch date; nothing was invented or added from memory, and one unverifiable term was omitted rather than guessed at. The complete provenance log lives in the site repository (spamTriggers.SOURCES.md). Terms without a citable source do not ship: that is a house rule across every dataset on this site.
Source: 188 Spam Words to Avoid: How to Stay Out of Spam Email Filters (ActiveCampaign), fetched 2026-07-14.
#1 · 100% more · 100% free · 100% satisfied · Additional income · Be your own boss · Best price · Big bucks · Billion · Cash bonus · Cents on the dollar · Consolidate debt · Double your cash · Double your income · Earn extra cash · Earn money · Eliminate bad credit · Extra cash · Extra income · Expect to earn · Fast cash · Financial freedom · Free access · Free consultation · Free gift · Free hosting · Free info · Free investment · Free membership · Free money · Free preview · Free quote · Free trial · Full refund · Get out of debt · Get paid · Giveaway · Guaranteed · Increase sales · Increase traffic · Incredible deal · Lower rates · Lowest price · Make money · Million dollars · Miracle · Money back · Once in a lifetime · One time · Pennies a day · Potential earnings · Prize · Promise · Pure profit · Risk-free · Satisfaction guaranteed · Save big money · Save up to · Special promotion
Source: 188 Spam Words to Avoid: How to Stay Out of Spam Email Filters (ActiveCampaign), fetched 2026-07-14.
Act now · Apply now · Become a member · Call now · Click below · Click here · Do it today · Don't delete · Exclusive deal · Get it now · Get started now · Important information regarding · Information you requested · Instant · Limited time · New customers only · Order now · Please read · See for yourself · Sign up free · Take action · This won't last · Urgent · What are you waiting for? · While supplies last · Will not believe your eyes · Winner · Winning · You are a winner · You have been selected
Source: 188 Spam Words to Avoid: How to Stay Out of Spam Email Filters (ActiveCampaign), fetched 2026-07-14.
Bulk email · Buy direct · Cancel at any time · Check or money order · Congratulations · Confidentiality · Cures · Dear friend · Direct email · Direct marketing · Hidden charges · Human growth hormone · Internet marketing · Lose weight · Mass email · Meet singles · Multi-level marketing · No catch · No cost · No credit check · No fees · No gimmick · No hidden costs · No hidden fees · No interest · No investment · No obligation · No purchase necessary · No questions asked · No strings attached · Not junk · Notspam · Obligation · Passwords · Requires initial investment · Social security number · This isn't a scam · This isn't junk · This isn't spam · Undisclosed · Unsecured credit · Unsecured debt · Unsolicited · Valium · Viagra · Vicodin · We hate spam · Weight loss · Xanax
Source: 188 Spam Words to Avoid: How to Stay Out of Spam Email Filters (ActiveCampaign), fetched 2026-07-14.
Accept credit cards · Ad · All new · As seen on · Bargain · Beneficiary · Billing · Bonus · Cards accepted · Cash · Certified · Cheap · Claims · Clearance · Compare rates · Credit card offers · Deal · Debt · Discount · Fantastic · In accordance with laws · Income · Investment · Join millions · Lifetime · Loans · Luxury · Marketing solution · Message contains · Mortgage rates · Name brand · Offer · Online marketing · Opt in · Pre-approved · Quote · Rates · Refinance · Removal · Reserves the right · Score · Search engine · Sent in compliance · Terms and conditions · Trial · Unlimited · Warranty · Web traffic · Work from home
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