Email subject-line length checker
Aim 40–60 characters. Agents that write 90-character subjects lose the verb.
Keep the verb visible on mobile
Agent-drafted subjects often run long. Count characters against a practical ~40–60 window so the action is still readable when the inbox truncates.
How to use the subject-line length checker
Type or paste the subject. Read the count and band, then shorten from the front so the verb stays early — especially for agent follow-up email.
Your subject
44
Good for most inboxes
What the band means
It is a heuristic for this tool, not a carrier guarantee. Preview important messages in your mail client and pair tagged links with the UTM builder when attribution matters.
FAQ
What character length does this checker recommend?
It treats about 40–60 characters as a practical window for many mobile inboxes: at or under 40 is “short,” 41–60 is “good for most inboxes,” and over 60 is flagged as likely to truncate on mobile. That band is a heuristic for this tool, not a universal carrier rule.
Why do long subject lines matter for agents?
Agents that draft long subjects often push the verb or the date past the fold on small screens. Keeping the action early in a shorter subject improves what the recipient actually sees.
Does character count equal rendered width?
No. Character count is a simple proxy. Wide characters, emoji, and client UI chrome still change what fits. Use the count as a first pass, then preview in your mail client when the message is high stakes.
Should every email aim for 40–60 characters?
Not always. Transactional subjects can be shorter; some brands prefer longer for desktop. Treat the band as a default for agent-drafted outreach, then adjust from open and reply data.
How does this fit with UTM-tagged links?
Subject length shapes whether the message gets opened; UTM tags on links inside the body shape attribution after the click. Use both when an agent sends campaign email.
Need agent email that stays readable and measurable?
GoWith agentic builds draft follow-ups with length and tagging constraints. See all free tools, the UTM link builder, the follow-up cadence planner, and the lead response time & SLA calculator.
Educational only. Not legal advice and not a substitute for testing the live agent. Email subject-line length checker runs in your browser — nothing is sent to your CRM unless you copy it yourself.