Email Subject Line Tester
100% PrivateMarketing ToolsScore an email subject line and preview how it looks in a crowded inbox.
Runs entirely in your browser. Your input is not uploaded to Ovatly or anywhere else.
Type a subject line and the checks run as you type. This is writing guidance based on common inbox behavior, not deliverability data: no tool can tell you whether a message will land in the spam folder.
- 1Type or paste your subject line; the analysis updates as you type.
- 2Look at the phone preview to see what survives truncation. Put important words first if the end is cut.
- 3Work through the heuristic checks and any style flags.
- 4Open the spam-flag word list if a match surprises you, and judge it in context.
Subject: "Your spring reading list is here" 32 characters, 6 words, reading grade estimate 0.5, no words from the spam-flag list, no style flags, and it fits the mobile range whole. All four heuristic checks pass.
- The spam-flag list is a heuristic built from words that appear in many published filter rule sets, and the tool shows it in full so you can disagree with it. One flagged word rarely matters; sender reputation, content and engagement matter far more.
- The reading grade is a Flesch-Kincaid estimate on a single fragment, so treat it as a rough plainness nudge, not a measurement.
- Emoji are counted as one character each, the way readers perceive them, even though some systems count them differently internally.
No tool can. Delivery depends mostly on your sending domain's reputation, authentication (SPF, DKIM, DMARC), message content and how subscribers have treated your past mail. This tester only reviews the subject line's writing.
About this tool
The Email Subject Line Tester runs the checks an experienced email marketer does by eye: character and word counts, how the line survives being cut down to the roughly 33 to 43 characters many phones show, flags for all-caps text, repeated punctuation, currency symbols and fake Re: prefixes, matches against a built-in list of spam-flag words, and a reading-grade estimate. Every result is labelled as guidance, because that is what it is: no checker can decide where your message lands, and this one says so.
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Part of Ovatly's free tools in Marketing Tools.