Email Subject-Line Length & Spam-Word Checker
Make sure your subject line fits the inbox and reads as trustworthy — a live length check for typical phone and desktop previews, plus a junk-word list.
Short enough to likely show in full on most phones
No words from our junk-mail list. This is a fixed word list, not a spam filter, and it does not predict deliverability: that rests on authentication (SPF, DKIM), your sending reputation and complaint rate.
The line that decides the open
The subject line is the whole pitch for whether an email gets opened, and it is judged in a crowded inbox in a fraction of a second, often on a phone that only shows the first few words. Length is the first constraint: keep the essential idea near the front so it survives the truncation on small screens.
The second constraint is trust. Wary readers react to the vocabulary of junk mail: urgency, money, and too-good-to-be-true promises. The word list here does not model any spam filter; where an email lands rests on your sending reputation, authentication and list health. Short, specific and honest subject lines respect the reader either way.
Frequently Asked Questions
How long should an email subject line be?
There is no single cut-off: it varies by email client, device and screen width. Many phones show roughly the first 35 to 40 characters and desktops about 60, so put the most important words first and let the subject still make sense if the tail is cut. The preview text shown after it can carry the rest.
What are spam-trigger words?
Words and phrases such as free, act now, cash bonus, guaranteed and click here that readers associate with junk mail. This checker's list is fixed vocabulary, not a spam filter, and it does not predict where an email lands: modern filters weigh sender reputation, authentication and how recipients react. Treat a listed word as a prompt to ask whether a plainer word says the same.
Will avoiding these words guarantee I reach the inbox?
No. Gmail's sender guidelines ask every sender for SPF or DKIM authentication and a spam rate reported in Postmaster Tools below 0.3%; they set no rule on subject-line words. Reputation, list quality and consent decide where mail lands. In the US the CAN-SPAM Act also requires a subject line that accurately reflects the message.
Why does the checker not flag 'free' inside 'freedom'?
It matches whole words, not fragments, so 'freedom', 'agree', or 'therapist' will not set off the filter for 'free', 'gree', or the like. This avoids false alarms and keeps the count meaningful — only genuine standalone trigger words and phrases are counted.
What makes a subject line get opened?
Relevance and curiosity, kept honest. Say something specific the reader cares about, hint at value without giving everything away, and never over-promise — a subject that oversells sets up disappointment and trains people to ignore you. Personal, clear, and concise beats clever and vague.
Educational guide only. Inbox truncation and spam filtering vary by client and provider; deliverability depends on many factors beyond the subject line, so test with your own audience.