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In Gmail on the web, start your reply, click the small down arrow beside Reply (or Reply all), choose Edit subject, and enter the new subject. This changes the subject of the message you are sending; it does not rename the original email or automatically change its recipients.
Change the subject while replying in Gmail on a computer
- Open Gmail in a web browser and open the message or conversation.
- Click Reply or Reply all.
- In the reply composer, click the small down arrow beside the response type (the control that may display Reply).
- Select Edit subject.
- Replace or revise the subject in the subject field.
- Review the To, Cc and Bcc fields, along with the message body, quoted text, signature and attachments.
- Click Send.
Google documents this control in its Gmail and Workspace reply instructions: Gmail web reply and recipient instructions. The menu is attached to the reply action, not necessarily to the message’s main three-dot More menu.
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What the subject change actually does
It changes only the outgoing reply
The received message keeps its original subject. Gmail does not retroactively rename that message or rewrite the conversation history.
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Choosing Edit subject changes the subject field rather than automatically deleting the quoted conversation. You can remove irrelevant quoted text manually before sending.
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It does not change recipients
Changing a subject has no effect on who receives the message. Reply addresses the sender (and any recipients Gmail includes for that reply); Reply all can include everyone on the original recipient list. Remove unnecessary or confidential addresses before sending.
It is not a guaranteed thread reset
A changed subject may cause Gmail or another mail app to display the reply as a separate conversation, but mail systems can also use message headers and other threading information. Gmail, Outlook, Apple Mail and other clients may group the message differently. Treat a subject change as a clear topic signal, not as a universal command to start a new thread.
Reply or Reply all: which should you use?
The subject control is available from either reply mode, but the delivery consequences differ.
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- Use Reply when only the sender (and any deliberately added recipient) needs the changed-topic response.
- Use Reply all only when every original participant should see the new subject and message.
- Inspect each address after selecting the response mode. A new subject does not protect you from sending internal or sensitive information to an old recipient.
Change the subject in the Gmail Android app
Google’s Android Workspace guidance shows the same Edit subject command, although the exact layout can vary by app version, account type and message view.
- Open the Gmail app and the relevant message.
- Start a reply.
- Look for the response-type control or its drop-down menu near the reply composer.
- If Edit subject appears, tap it and enter the new subject.
- Check recipients and content, then send.
If the command is not visible, use Gmail in a desktop browser or create a new message instead. The Android instructions are documented at Google’s Android Gmail guidance.
iPhone and iPad: what to do when the control is missing
Google’s published help does not establish one universal, current Edit subject path for every Gmail iOS screen. The option may be absent or presented differently in the app you have.
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- Open Gmail in a desktop browser and use Reply → response-type arrow → Edit subject.
- From a mobile browser, request the desktop version of Gmail if that option is available.
- Start a new message and manually choose the recipients, subject and any context you want to include.
When a new message is safer
Use Compose when the topic is genuinely separate, the recipient list must be rebuilt, or the old quoted history is irrelevant or confidential. Gmail’s compose window provides dedicated recipient and subject fields; Google describes the workflow in its message-composing help.
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- Add the intended recipients.
- Enter the independent subject.
- Write the message and add only appropriate attachments or quoted material.
- Review the addresses and send.
A new message gives you the most reliable separation across different mail clients because it does not rely on how a client interprets a reply’s threading headers.
Reply, new message or forward?
| Method | Best for | Main caution |
|---|---|---|
| Edit subject in a reply | A related topic where existing context and recipients still matter | The message may remain connected to the old conversation in some clients |
| Reply all, then edit subject | A related topic that every original participant should receive | Old recipients may see a topic that no longer concerns them |
| New message | Clean topic separation, a rebuilt recipient list or removal of old history | You must select recipients and decide what context to include again |
| Forward | Passing the original message, attachments or formatting to someone new | The forwarded content may reveal more of the original exchange than intended |
Troubleshoot a missing “Edit subject” option
You have not started a reply
The subject command appears inside the reply composer. Open the message and click Reply or Reply all first.
You opened the wrong menu
Do not rely on the message’s main three-dot menu. Look beside the response-type label in the composer for its small down arrow.
The composer is collapsed
Expand the inline reply box so its controls are visible. A narrow browser window can also hide part of the composer; widen it or open the message in a desktop browser.
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You are in a mobile or non-Gmail app
Mobile interfaces and third-party mail apps do not always expose the same control. Try Gmail on the web, or use Compose for an independent message.
You are trying to edit the received email
The original message’s subject cannot be changed from your mailbox. Only the subject of the outgoing reply can be edited.
Checks to make before sending
- Confirm whether you selected Reply or Reply all.
- Inspect To, Cc and Bcc, removing anyone who no longer belongs on the conversation.
- Read the quoted history and delete sensitive or unrelated material.
- Verify that attachments are still appropriate for the new topic.
- Make sure the new subject accurately describes the message.
- If the subject change marks a separate issue, consider adding a short transition such as “Changing the subject because this is a separate issue.”
For Google’s consumer explanation of changing a subject in a reply, see Gmail reply help.
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