You can edit a Gmail subject line up to 30 seconds after sending

Gmail lets you change the subject line of a message you just sent, but only if you act within about 30 seconds. After that window closes, the subject is locked and cannot be changed. This feature is called Undo Send, and it works by holding your message in an outbox for a few seconds before it actually leaves your account.

If more than 30 seconds have passed, you cannot edit the subject of a sent message. Your only option at that point is to send a new message with the correct subject and ask the recipient to disregard the first one. This guide covers both the quick fix and what to do when you have missed the window.

Key Takeaways

  • The Undo Send feature must be turned on in Gmail settings before you can use it, and it is not enabled by default.
  • After you hit Send, a popup appears at the bottom of the screen with an Undo button — click it within 30 seconds to get your message back and edit the subject.
  • You can change the Undo Send window from 5 seconds to 30 seconds in Gmail settings under General.
  • Once the undo window closes or if you did not enable the feature, you cannot change a subject line on a message that has already been sent.
  • If you missed the window, send a follow-up message with the correct subject and ask the recipient to use that one instead.

Turn on Undo Send in Gmail settings

Undo Send is not turned on by default in Gmail, so you need to enable it first. Open Gmail in your web browser and look for the gear icon in the top right corner of the screen. Click it and select See all settings from the dropdown menu.

In the Settings page, stay on the General tab, which opens automatically. Scroll down until you see the section labeled Undo Send. You will see a checkbox next to "Enable Undo Send" — click it to turn the feature on. Below that checkbox is a dropdown menu that lets you choose how many seconds you want the undo window to stay open. The options are 5, 10, 20, or 30 seconds. Most people choose 30 seconds to give themselves the most time to catch mistakes. After you make your choice, scroll to the bottom of the page and click Save Changes.

Edit the subject line within 30 seconds of sending

Once Undo Send is enabled, compose your message as you normally would. When you click the Send button, your message does not leave immediately. Instead, a notification appears at the bottom left of your screen that says "Message sent" with an Undo button next to it. You have until the countdown timer runs out — usually 30 seconds if you set it to maximum — to click Undo.

Click the Undo button and your message returns to the compose window exactly as you wrote it. The subject line, body text, attachments, and recipient list all come back. Make whatever changes you need, including fixing the subject line. When you are done, click Send again. This time the message will go out with the corrected subject.

What to do if you missed the undo window

If 30 seconds have passed and the undo notification has disappeared, the message has been delivered and you cannot change the subject line. At this point, your best option is to send a new message to the same recipient with the correct subject line. In the body of the new message, write something like "Please disregard my previous message with the subject [wrong subject]. Use this message instead."

This approach works well for most situations, especially if the recipient has not yet read the first message. If the message was sent to a group or a mailing list, you may want to send the follow-up to the same group so everyone sees the correction. Keep the follow-up brief and professional — you do not need to explain in detail what went wrong, just make it clear which message to use.

Undo Send does not work on mobile Gmail

The Undo Send feature only works when you use Gmail in a web browser on a computer. If you use the Gmail app on your phone or tablet, you will not see the Undo button after you send a message, even if you have the feature turned on in your web settings. Mobile Gmail sends messages immediately without the delay that the web version uses.

If you need to change a subject line and you are using Gmail on your phone, your only option is to send a follow-up message with the correct subject. Consider switching to a computer or waiting until you can access Gmail in a browser if you are worried about sending a message with the wrong subject.

How to prevent subject line mistakes before sending

The easiest way to avoid needing to undo a message is to check the subject line before you click Send. Make it a habit to read through the entire compose window — recipient, subject, and body — before sending anything. Many mistakes happen when you are typing quickly or switching between multiple messages.

If you often forget to add a subject line, Gmail can remind you. In Settings under the General tab, scroll down to find Compose settings. Look for an option that says "Warn me if I forget to add a subject line" and make sure it is checked. When this is on, Gmail will show you a warning if you try to send a message with no subject, giving you a chance to add one before the message leaves your account.

Frequently Asked Questions

Can I undo a message I sent to the wrong person?

Yes. Click Undo within your time window and the message returns to the compose screen. You can then change the recipient before sending it again. This is one of the most useful reasons to have Undo Send turned on.

What happens if I undo a message and then close the browser?

The message stays in your Drafts folder. When you open Gmail again, you will find it there ready to edit and send whenever you want. You do not lose the message by closing your browser.

Does Undo Send work on forwarded messages?

Yes. You can undo a forwarded message the same way you undo a regular sent message — click the Undo button within your time window and make any changes you need before sending it again.

Can I change the recipient after I click Undo?

Yes. When you click Undo, the entire message returns to the compose window, including the recipient field. You can change who you are sending it to, the subject, the body, or anything else before you send it again.

Why does my Undo button not appear after I send?

The most common reason is that Undo Send is not turned on in your settings. Go to Settings, click the General tab, and look for the Undo Send section. Make sure the checkbox next to "Enable Undo Send" is checked. If it is already checked, try logging out of Gmail and logging back in.