Email Subject Preview

See roughly where each mail client cuts your subject line off, and what shows up beside it.

Runs on your deviceEmailWorkingNo account needed

What this tool does

Email Subject Preview counts the characters in a subject line and lays it against the display limits of ten desktop and mobile clients — around 78 for Apple Mail on macOS, 70 for Gmail on the web, 41 for iPhone Mail held upright, 33 for Samsung Mail on Android. Each row of the inbox preview shows the subject as that client would leave it, with an ellipsis where the text runs out, so you can read which words survive instead of inferring it from a subject length figure.

The preheader covers the other half of the inbox row. Type the first line of your body copy and it appears after the subject on the clients that display a snippet: Outlook on Windows and Samsung Mail are recorded as not showing one, and on the rest it only appears while the subject still leaves room. Each subject is also checked for the things that read badly in a list — anything past 60 characters, shouty capitals, two or more exclamation marks, repeated punctuation, more than two emoji, a leading Re:, Fw: or Fwd:, prices and percentages, invisible zero-width characters, and phrases drawn from a fixed list of well-worn promotional wording. Those notes appear as a list under the table, one set per subject.

Two limits are worth knowing before you trust a row. These are character counts, while real clients wrap by pixel width in a proportional font, so a line of narrow letters survives further than the table suggests and a line of capitals is cut sooner; read the limits as approximate and the ranking between clients as the durable part. And the wording check is a word list, not a spam filter. It is matched as plain substrings, so a subject about freedom trips the entry for free and one about cashflow trips the entry for cash, and it knows nothing about your sending reputation, your authentication records or the body of the message — a subject with no notes against it is not a prediction that the mail arrives. Nothing here is uploaded: the subjects, the preheader and the results are worked out in this browser tab.

How to use it

  1. Type your subject lines. One per line, so several drafts are measured in the same table. Load sample fills in three subjects: two that trip the wording checks and one that clears them.
  2. Add the preheader. Optional, and only used by the clients that show a snippet. Paste the real opening line of the body rather than a summary of it.
  3. Choose which clients to show. All ten, mobile only, or desktop only. Mobile is where subjects are cut hardest, so it is the stricter of the two tests.
  4. Read the Result column. Every row is marked as fitting or cut at its limit, and the summary counts how many of the subject-and-client combinations were truncated.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

Writing a campaign subject

The interesting half of a long subject usually sits past the 35 characters the Gmail app shows. The table says what is left of it.

Deciding what belongs in the preheader

If the offer is cut from the subject on a phone, moving it into the snippet keeps it visible rather than losing it entirely.

Checking a transactional template

Truncation always takes the end, so an invoice or receipt subject that finishes with the reference number loses the useful part first.

Comparing several drafts

Paste four candidate subjects at once and each gets its own block of rows, with its character count and warnings in the notes below. The summary gives one truncation total for the whole run rather than ranking the drafts, so the comparison is yours to read off the blocks.

Auditing a subject built from merge fields

A line wrapped around a customer or company name changes length with every recipient. Paste the longest real name, not the placeholder.

Questions

Is anything uploaded?
No. The subject lines, the preheader and the whole table are produced in this browser tab, so unreleased campaign copy stays on your machine and the tool still works with the network off.
Are the character limits exact?
No, and no tool's can be. Clients cut by the pixel width available in a proportional font, which shifts with window size, font size and device, so the same 45 characters can fit in one inbox and not another. The figures used here are the commonly cited averages, and the sender name that shares the row is not modelled at all.
Will this tell me whether I land in spam?
No. The notes flag wording that reads as promotional — a fixed list of phrases, plus capitals, exclamation marks and emoji counts. Filtering rests mainly on authentication, sending history and how recipients have treated your mail before, none of which a subject line reveals.
Why is the preheader missing from some rows?
Two reasons. Outlook on Windows and Samsung Mail on Android are listed as showing no snippet, and on the remaining clients the snippet is dropped once the subject has been cut, because there is no room left beside it.
How are emoji counted?
Characters are counted by code point, so a plain emoji counts as one, while a flag, a skin-tone variant or a family sequence is assembled from several code points and counts as several — a subject using those looks longer here than it will in an inbox. The separate emoji tally counts only pictographic code points, which makes a family sequence read as three emoji and a flag as none; and because the joiners holding a family sequence together are invisible characters, that subject also picks up the zero-width warning it does not deserve.
Can I check several subjects at once?
Yes. Put one per line and each is measured against every selected client. It is the quickest way to see what a shorter rewrite actually buys you.
Does it show the message itself?
No, only the row in the list. Use HTML Email Preview to render the body at different widths, and Email Size Estimator to work out how heavy the message will be with its attachments.

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