How to use the Email Subject Line Tester
- 1. Type the subjectAdd the preheader (preview text) too if your email has one.
- 2. Test itSee each check pass or fail with a short reason.
- 3. Improve and A/B testFix the flagged items, then test two versions on your list.
Worked example
The sample subject, Your free Python roadmap (with 30 practice tasks), is 49 characters and 8 words. It passes the 20–60 character length check but is longer than the roughly 40 characters many phones show, and it contains free, which is on our list of words common in spam. The score is 85 / 100: 100 minus 5 for the phone preview and 10 for one spam-style word. The 59-character preheader adds information instead of repeating the subject, which is good.
Remove the word free, or move "30 practice tasks" to the front, and the score rises.
What the score can and cannot tell you
- It is a checklist of common best practices: length, shouting, punctuation, emoji, honest RE: and FWD:, and words that often appear in spam.
- Spam filters judge the whole email, your sending domain and your reputation, not one word. A clean subject does not guarantee the inbox.
- No tool can predict open rates for your audience. Only an A/B test on your list can.
- Apple Mail Privacy Protection inflates opens, so judge tests by clicks too.
Short acronyms such as SQL, HTML, GST and UPI are not counted as shouting. Emoji are counted with Unicode pictograph rules. Measure campaign results with the email open rate calculator and build the email with the HTML email template builder.
Frequently asked questions
What is a preheader?
The short preview text shown after the subject in most inboxes. If you do not set one, the inbox shows the first text in the email, often 'View in browser'.
Are emoji good in subject lines?
One relevant emoji can stand out; several look spammy and some older email apps show boxes instead.
Is the Email Subject Line Tester free?
Yes, the Email Subject Line Tester is free. The first time you test your first subject line, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.