Tools / Email subject line checker
Check a subject line before you send it.
Length on desktop and mobile, how it pairs with your preview text, and the formatting habits that get mail filtered. Facts, not a score.
Inbox preview
Your company
Your subject line appears here
Your preview text appears here
How to use this well
There is no score here on purpose. Tools that rate a subject line out of 100 are inventing a number, and nobody can predict your list's open rate from the text alone. What is measurable is length, capitalization, punctuation and known filter-trigger words.
Mobile mail apps show roughly 35 to 40 characters. Desktop shows more. Front-load the part that matters, because the end of a long subject line often is not read at all.
Preview text is the second line most clients show. Leaving it empty means the client fills it with whatever your email starts with, which is often an unsubscribe link or an image alt tag.
This runs entirely in your browser. Nothing you type is sent anywhere or stored.
Common questions
Will avoiding these words guarantee inbox placement?
No, and any tool that says otherwise is overselling. Deliverability is mostly about your sending domain's reputation, authentication, and whether people engage with your mail. Word choice is a small factor, not the main one.
Should I use emojis in subject lines?
They render inconsistently across mail clients and can look broken. Test with your own list before committing to them.
How do I actually know what works?
Send two versions to matched halves of your own list and compare. Your list is the only benchmark that applies to your list.