Subject Line Tester: Preview Your Subject and Preview Text
Type your subject line and preview text to see how they'll look, and where they'll be cut off, in iPhone Mail, the Gmail app, Gmail on a computer and Outlook. Tips update as you type.
How it looks
Previews use each app's typical width and font size, so the cut-off point is close to what readers see. Exact results vary with screen size, text size settings and the reader's other emails.
Tips for subject lines and preview text
Put the important words first. Phones show roughly 30–45 characters of a subject line before cutting it off.
Always write preview text. If you don't, the inbox shows the first words of your email instead, which is often "View in browser" or an image's alt text.
Avoid ALL CAPS, piles of !!! and spammy phrases. They look pushy to readers and to spam filters alike.
How to use the Subject Line Preview
- Type the sender name your readers will see.
- Write your subject line and preview text.
- Check the four inbox previews to see where each is cut off.
- Follow the tips under the boxes, then adjust until the important words show everywhere.
Writing subject lines that get opened
Lead with the reason to open: the offer, the news, or the question, in the first 30 to 40 characters.
Be specific: "Your order ships Tuesday" beats "An update about your order".
Use the preview text as a second line of your pitch rather than repeating the subject.
Test two versions on a small part of your list if your email platform supports it, then send the winner to everyone else.
Why preview text matters
Most inboxes show a line of preview next to or under the subject. If you don't set one, the inbox fills it with whatever comes first in your email, which is often "View this email in your browser" or an image description.
Related free tools
See also: Writing the preview line? See 40 preheader examples. Unsure about capitals or emojis? Read subject line capitalization and emojis in subject lines.
What the subject line tester does
This tester shows how your sender name, subject line and preview text will look in four common inboxes: iPhone Mail, the Gmail app, Gmail on a computer and Outlook on a computer. You can see where the words get cut off before you send, and get simple tips as you type, so the part that makes people open your email is actually visible.
Benefits
- Four inbox previews at onceSee your email as it might appear in iPhone Mail, the Gmail app, Gmail on a computer and Outlook, side by side, updating with every keystroke.
- Character and word countsLive counters show subject length, preview text length and word count, colored green, amber or red against common length guidelines.
- See what happens with no preview textLeave the preview field empty and the mockups show the kind of filler line inboxes use instead, so you can see why it matters.
- Tips that respond to your wordsThe tool tells you when your subject is likely cut off on phones, when preview text is too short, or when it just repeats the subject.
- Spots spam-like habitsIt flags ALL CAPS subjects, several capitalized words, repeated !! or ??, and common spam phrases such as act now or click here.
- Warns about misleading prefixesStarting a marketing subject with Re: or Fwd: gets a warning, because it can hurt readers' trust.
- Test your sender name tooChange the sender name to see how it sits next to the subject, including the initial shown in the Gmail app's round avatar.
Who it is for
- A small-business owner writing a sale or announcement email who wants the offer to show on phones.
- A marketer comparing a few subject line ideas before setting up a campaign in Mailchimp or a similar tool.
- A nonprofit staff member writing a donation appeal who needs the key message in the first few words.
- A salesperson checking that an outreach subject line doesn't look like spam.
- A freelancer or agency showing a client how their email will look in the inbox before it goes out.
How to use it
- Type the sender name readers will see.
- Enter your subject line and preview text.
- Check the four inbox previews to see where each is cut off.
- Read the tips under the fields and adjust your wording.
- Copy your final subject and preview text into your email platform.
Your privacy
Everything you type stays in your browser and is only used to draw the previews on the page. Nothing is sent or saved.
Frequently asked questions
How long should an email subject line be?
Aim for 30 to 45 characters so the whole subject shows on phones, and put the most important words first.
What is preview text (preheader)?
The short line shown after or under the subject in the inbox. If you don't set it, inboxes show the first words of your email instead.
How long should preview text be?
Roughly 40 to 100 characters. Use it to add to the subject, not repeat it.
Do emojis work in subject lines?
Most modern inboxes show them, and the previews here use your device's emoji. Use them sparingly and never in place of the key words.
How do I set preview text?
Most email platforms have a "Preview text" or "Preheader" field next to the subject line. If yours doesn't, add a short hidden line at the very top of your email.
Do subject lines get cut off on computers too?
Less often, but Gmail on a computer shows the subject and preview text on one line, so long subjects push the preview text out of view.