Email Subject Line and Preview Text Checker with an inbox preview
Test up to four subject lines and preview texts side by side, with an inbox sketch and checks.
- Free to use
- Runs in your browser
- No sign-up
Type a subject line to check it
A phone and desktop inbox sketch, the length, capitals, emoji, Re: and Fwd:, merge tags and claims that need proof appear here as you type. Or press Try an example.
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About the Email Subject Line Checker
Type your sender name and up to four versions of a subject line and preview text, for a newsletter, an offer or an announcement. You see each version in a sketch of a phone inbox and a desktop inbox, with where the lines are cut (our measure), and a table of the versions side by side. Each version is checked for length, words in capitals, exclamation marks and emoji, emoji that look like a verified badge or a warning, a misleading "Re:" or "Fwd:", leftover text and merge tags in the preview, and claims such as "No. 1", "free" or "last chance" that Indian advertising rules ask you to back up. Every check says whether it comes from Gmail's sender guidelines, an Indian rule or our checklist. It runs in your browser with fixed rules: it does not write subject lines, send email or predict opens.
How it works
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01
Type the sender name your readers see, then the subject line and preview text of version A. Add more versions to compare, or try the example.
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02
Look at the phone and desktop sketch to see what shows before each line is cut, and at the table to compare the versions.
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03
Pick a version to read its checks and fixes, change the wording, and copy the comparison to share it with your team.
Gmail's rules for subject lines and sender names
Gmail's sender guidelines say subject lines, headers and display names should match the real sender and content. They ask senders not to start a subject with Re: or Fwd: unless the email really is a reply or a forward, and not to use emoji or other characters to imitate graphic elements, for example to suggest the sender is verified. The display name should clearly identify the sender, without emoji or subject wording; Gmail's examples of names to avoid include "URGENT REQUEST" and "Last Chance". Gmail does not publish a list of spam words, so this tool has none.
Claims in a subject line are advertising claims
ASCI's Code covers e-mail, and the Consumer Protection Act, 2019 counts publicity on electronic media and the internet as advertising. ASCI asks that claims of fact can be substantiated, the CCPA's 2022 guidelines have rules on "free" claims, and its 2023 dark patterns guidelines list false urgency. So the tool flags "No. 1", "best", guarantees, "free", deadlines and discounts, with what to show in the email to back them up. The word lists are the same as in our Claims and Sources Checker.
What this tool cannot do
It cannot tell you which version people will open: the score is our checklist, not a forecast. Where each line is cut depends on the app, the font and the screen, so the sketch and the cut points are our measure, as are the lengths (up to 60 characters for a subject line, 35 to 110 for preview text). It does not send email, check your domain or read the rest of your email, and it is not legal advice. Send a test to yourself before every campaign.
Frequently asked questions
How long should an email subject line be?
There is no official limit for inboxes. Our measure is up to 60 characters with the words that matter first, because a phone shows only the first part: in our sketch of a phone about 360 pixels wide, that is often 30 to 40 characters. The tool shows where each of your versions is cut.
What is preview text?
It is the line many inboxes show after the subject line, also called preheader text. You set it in your email tool. If you leave it empty, many inboxes show the first words of the email instead, which may be a "view in browser" line. Our measure is 35 to 110 characters, adding something the subject does not say.
Can I start a marketing email with "Re:" to get more opens?
No. Gmail's sender guidelines ask senders not to start a subject line with Re: or Fwd: unless the email really is a reply or a forward, and Gmail's bulk email advice says deceptive subject lines are against its policy. The tool marks it as something to fix.
Are emoji in subject lines a problem?
One or two that add meaning are fine on our checklist; check how they look on a phone. Gmail asks senders not to use emoji or other characters to imitate graphic elements in a way meant to deceive, such as a tick that suggests a verified sender, so the tool flags ticks, locks, warning signs and mail icons.
Does the tool check for spam words?
No. Gmail does not publish a list of words that send email to spam. Its sender guidelines focus on sending only to people who signed up, setting up email authentication (SPF or DKIM, and DMARC too for bulk senders), easy unsubscribing and not misleading people. Check your domain's set-up with our Email Deliverability Checker.
Sources and checks
Rules last checked
The Email Subject Line Checker follows these official pages:
- Email sender guidelines (support.google.com)
- The ASCI Code (ascionline.in)
- Guidelines for Prevention of Misleading Advertisements and Endorsements for Misleading Advertisements, 2022 (pib.gov.in)
- The Guidelines for Prevention and Regulation of Dark Patterns, 2023 (consumeraffairs.gov.in)
Gmail publishes no list of spam words, so the tool has none; the score and the lengths are our own measures.
Scores, limits and suggestions marked "our checklist", "our measure" or "our suggestion" are ours, not Google's or the platform's. How our tools work
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