You can't change a subject line after you send an email in Gmail, but you can unsend it within 30 seconds and resend with the correct subject

Gmail does not have a feature to edit the subject line of an email after it leaves your outbox. Once you hit send, the subject is locked. Your only option is to use Gmail's Undo Send feature, which gives you a brief window to pull the email back and resend it with a new subject line.

The undo window is short — typically 5 to 30 seconds depending on your Gmail settings — so you need to act fast. If you miss that window, the email is delivered and cannot be changed. The recipient will see the original subject line.

Key Takeaways

  • Gmail's Undo Send feature lets you recall an email for up to 30 seconds after you press send, giving you time to fix the subject line.
  • You must enable Undo Send in Gmail settings first; it is not turned on by default for all accounts.
  • Once the undo window closes, the email is delivered and the subject cannot be changed.
  • If you miss the undo window, your only choice is to send a follow-up email with the correct subject and ask the recipient to disregard the first one.

How to enable Undo Send in Gmail settings

Open Gmail and click the gear icon in the top right corner, then select See all settings. Scroll down to the section labeled Undo Send. You will see a dropdown menu with time options: 5 seconds, 10 seconds, 20 seconds, or 30 seconds. Choose the duration that works for you — 30 seconds gives you the most time to catch a mistake.

Click Save Changes at the bottom of the page. The setting takes effect immediately. From now on, when you send an email, a bar will appear at the top of your inbox with an Undo button and a countdown timer showing how many seconds you have left.

How to use Undo Send to fix a subject line

After you click send, watch for the undo bar to appear at the top of your inbox. It will show a message like "Message sent" with an Undo button next to it. Click Undo before the timer runs out. The email will return to your drafts, and the compose window will open automatically.

Click on the subject line field and change it to what you meant to write. Make any other corrections you need, then click Send again. The email will go out with the new subject line. The recipient will receive only the corrected version.

What happens if you miss the undo window

If the timer runs out or you do not notice the undo bar in time, the email is delivered and cannot be recalled. Gmail does not offer a way to edit or delete an email that has already reached the recipient's inbox.

Your only recourse is to send a follow-up email to the same recipient with the correct subject line. In the body, briefly explain that your previous email had an incorrect subject and direct them to the new one. Keep it short — something like "Please disregard my last email; I'm resending with the correct subject line" — so the recipient knows what happened.

Why Gmail does not allow subject line edits

Email is a delivered message, not a document you can edit after it arrives. Once an email reaches someone's inbox, it becomes their copy of the message. Allowing senders to change subjects after delivery would create confusion about what the email actually says and could be used to mislead recipients about the content.

Gmail's Undo Send is a compromise: it lets you catch mistakes in the seconds right after you send, before the message actually reaches the recipient's server. After that window closes, the email is considered delivered and final.

Tips to avoid subject line mistakes

Read your subject line out loud before you send. Many people write the subject last, after composing the body, and miss typos or incomplete thoughts. Pause for a second and scan it the way the recipient will see it.

If you are sending to someone important or in a formal context, draft the email in a text editor first, then paste it into Gmail. This gives you a chance to review everything — subject, body, and recipient — before you commit to sending. It takes an extra 30 seconds and can save you from sending an email with "FW:" still in the subject or a half-finished thought.

Frequently Asked Questions

Can I undo an email I sent to the wrong person?

Yes, if you catch it within your undo window. Click the Undo button and the email returns to drafts. You can then delete it or send it to the correct recipient instead. This is one of the most common uses for Undo Send.

Does the recipient see that I undid an email?

No. If you undo before the timer runs out, the recipient never sees the email at all. It is as if you never sent it. They will only see the corrected version if you resend it.

What if my undo window is set to 5 seconds and I need more time?

Go back to Gmail settings, find Undo Send, and change it to 30 seconds. The new setting applies to all emails you send going forward. You cannot extend the timer on an email you have already sent.

Can I undo an email on my phone?

Yes, the Undo Send feature works the same way on the Gmail mobile app as it does on desktop. After you send, look for the undo bar at the bottom of the screen and tap Undo before the timer expires.