Email subject line tester
Type your subject line and preview text. See where Gmail, Apple Mail and Outlook cut them off, and what to fix.
Fits in all 4 apps.
Gmail app shows “Take another look at the item you left i…” (40 of 52 characters)
Tags like {{ first_name }} or *|FNAME|* are filled in with a sample name.
In the inbox
Typical widths, not exact: screen size, text size and app settings change what fits. Shown as a new, unread email.
On a computer this is one line. It wraps here to fit your screen.
Subject: all 33 charactersPreview: first 41 of 52 characters
Subject: all 33 charactersPreview: first 40 of 52 characters
Subject: all 33 charactersPreview: all 52 characters, then text from your email
Subject: all 33 charactersPreview: all 52 characters
How these rows are measured
We measure your words in a font like each app’s, at its usual size, and fit them into a typical width: 480 pixels for Gmail’s one-line subject and preview on a laptop-size screen, a phone 375 points wide for the Gmail app and Apple Mail, and new Outlook’s message list with the reading pane on the right. These widths make everyday text cut close to the counts Litmus, Email on Acid and Campaign Monitor publish (see the table below).
If your device doesn’t have an app’s own font, we use the closest one it has, so results can differ by a few characters. A dashed box marks space an app fills with text from inside your email.
Checks
Note: Preview text cut off in 2 of 4 apps
52 characters. Gmail app shows “Take another look at the item you left i…”
What to do: Put the most useful words first.
Looks fine: Subject fits in all 4 apps
33 characters, 6 words. Every app here shows the whole line.
What to do: Bigger text sizes show less, so keep the key words first.
Also checked, nothing to fix: sender name, Re: or Fwd:, capital letters and repeated marks.
Free. No signup. Your text stays in this browser.
How inbox previews work ↓How long should a subject line be?
Keep the words that matter in the first 35–40 characters — that’s what an iPhone shows (Litmus, Campaign Monitor). Gmail on a computer fits about 70.
Each app gives the subject a different amount of room, and on a phone it gets a single line. Letters aren’t all the same width, either. “WWW” takes more room than “iii”, and an emoji takes more than a letter. That’s why this tester measures your words instead of only counting them. Lead with the product or the offer, so a cut-off line still makes sense. For cart reminders, borrow from these 8 subject lines that name the item.
| Email app | Subject line | Preview text |
|---|---|---|
| Apple Mail on iPhoneLitmus, Campaign Monitor, Email on Acid, Apple | 35–41 characters | About 84 characters, over 2 lines by default |
| Gmail on a computerCampaign Monitor, Litmus | Up to about 70 characters | Shares the subject’s line, so a long subject leaves less room |
| OutlookLitmus, Email on Acid | About 20–30 characters in Outlook 2019; new Outlook, drawn above, shows about 30–35 | About 50 characters |
| Phones, all appsEmail on Acid | — | 30–80 characters |
| Webmail, all appsEmail on Acid | — | 40–120 characters |
These counts come from different devices and years, so they overlap rather than agree. Bigger text sizes and narrower screens show less.
What is preview text?
Preview text, also called a preheader, is the short line an inbox shows with the subject. Leave it empty and apps pull in the first part of your email instead, which Mailchimp notes can be a “View in browser” link or code. A short preview has the same problem: Litmus and Email on Acid both say apps keep reading into your email to fill the space. Use it to add something the subject leaves out, like these six preheader examples.
Give personalization tags a fallback
Tags like {{ first_name }} or *|FNAME|* are swapped for each person’s details when the email goes out. If someone has no first name on file and the tag has no fallback, it is left blank: “Hi , your cart is waiting.” Mailchimp lets you set a default value, such as “Friend”. In Klaviyo you can write it into the tag: {{ first_name|default:'there' }}. Or write a line that works without a name.
Test before you send
The rows drawn here use typical widths. Real inboxes change with screen size, text size, settings and fonts. Send yourself a test and open it on a phone and a computer, in the apps your readers use. Read the sender, subject and preview together. Then check the whole email with our free email reviewer. Writing lines with AI? Give it the facts first.
What this tester doesn’t do
It doesn’t give a score or predict opens. It doesn’t check for “spam words” either, because no reliable list exists: Litmus calls spam trigger words mostly a myth, since filters weigh your sending reputation and how people engage with your email. Gmail’s sender guidelines note that spam reports from readers can lower your domain’s reputation over time. Your subject should still say what the email is about: in the US, the CAN-SPAM Act requires it.
Sources
- Campaign Monitor: How to optimize your email subject line length 2021. About 41 characters on an iPhone, up to 70 in Gmail.
- Litmus: 8 embarrassing preview text mistakes 2017. iPhone Mail shows 35–40 subject characters and about twice as many of preview text.
- Litmus: Microsoft Outlook 2019, what’s new 2018. Plan for about 20–30 characters.
- Litmus: The ultimate guide to email preview text 2024. Short preview text is followed by more of the email; in Gmail the subject and preview share one line.
- Email on Acid: Preheader text 2023. 30–80 characters on phones, 40–120 in webmail, about 50 for Outlook, 84 in iPhone Mail.
- Email on Acid: Emoji and special characters in subject lines 2020. Emoji can show in color on an iPhone and in black and white in Outlook.
- Apple: Check your email in Mail on iPhone Two lines of preview by default, up to five in Settings.
- Mailchimp: About preview text Without preview text, apps show the first part of the message.
- Mailchimp: Set default merge values
- Klaviyo: How to add a first name to an email
- Google: Email sender guidelines Re: and Fwd:, sender names, and how spam reports affect reputation.
- Litmus: Why spam trigger words are a thing of the past 2021.
- Campaign Monitor: Subject line recommendations Capitals can read as yelling; no more than 3 exclamation or question marks.
- FTC: CAN-SPAM Act compliance guide A subject line must reflect what the message is about.
Subject line questions
See six preheader examples →How many characters of a subject line show on an iPhone?
About 35 to 41 in the Mail app on an iPhone held upright: Litmus puts it at 35 to 40, and Campaign Monitor suggests 41. That is one line. Wide letters, emoji, a bigger text size or a smaller screen fit fewer. The Apple Mail row above measures your own words.
Do emoji hurt deliverability?
We can’t give a simple yes or no, so this tester doesn’t guess. Filters weigh many signals together, mostly your sending reputation and how readers respond. What we can say: emoji look different in each app, some apps show them in black and white, and screen readers read their names aloud. Google also asks senders not to use emoji to mislead, such as a check mark next to a brand name to suggest it is verified.
Does this tool save or send what I type?
No. Everything runs in your browser. Nothing you type is uploaded, saved or sent. Use “Copy both lines” to keep your text.