Email Subject Line Checker & Preview
Check email subject line and preheader length, then preview how the message may appear in a recipient inbox.
Subject line review
Use the counts and inbox preview to refine the subject before sending.
Enter an email subject line to check its length and preview how it may appear in an inbox.
Email apps show different amounts of subject and preheader text depending on device, screen size, font settings, and inbox layout. Treat the preview and length guidance as practical checks, not fixed delivery limits.
Check your email subject line before you send
Paste your subject line and optional preheader to review the text length and see a simple inbox-style preview.
Different email apps show different amounts of text, so there is no universal character limit that guarantees a perfect display everywhere.
Use the checker to spot unusually long or very short copy and to see whether the subject and preheader work together at a glance.
The preview is an approximation. Actual inbox rendering varies by email client, device, screen width, user settings, and whether the provider inserts other interface elements.
Review an email subject in three steps
You only need the subject line. Add a preheader and sender name when you want a more realistic preview.
Paste the subject line
Enter the exact subject line you plan to use in the campaign.
Add preview details
Optionally add preheader text and the sender name recipients will see.
Review the result
Check the character counts and inbox preview, then adjust the copy if it looks too long, too vague, or repetitive.
Example promotional email
Suppose you are sending an autumn promotion.
The checker shows the subject and preheader counts separately and displays them together in an inbox-style row so you can judge the message at a glance.
What to look for before sending
Length is only one part of a useful subject line. Clarity and the relationship between the subject and preheader matter too.
Make the subject understandable
Recipients should be able to understand the main point without relying entirely on the preheader.
Use the preheader for extra context
Avoid simply repeating the subject. Use the additional space to add a benefit, deadline, detail, or next step.
Expect truncation
Longer text may be cut off in smaller inbox layouts. Put the most important information early.
Recognize the sender
A clear sender name can be just as important as the subject because recipients decide quickly whether a message looks familiar and relevant.
Email subject line checker questions
Common questions about subject lines, preheaders, and inbox previews.
What is the ideal email subject line length?
There is no single length that displays perfectly in every inbox. Different clients and devices show different amounts of text. Use the character count as a practical warning, not a fixed rule.
What is preheader text?
Preheader text is supporting copy that many email apps show beside or below the subject line before the email is opened.
Should the preheader repeat the subject?
Usually it is more useful to add context, a benefit, a deadline, or another reason to open rather than repeat the same words.
Does this predict open rate?
No. The checker reviews text length and presentation only. Open rates are affected by audience quality, sender recognition, relevance, timing, deliverability, offer strength, and many other factors.
Will the preview look exactly the same in Gmail or Apple Mail?
No. The preview is a simplified inbox-style reference. Actual rendering depends on the email app, device, screen width, and user settings.