The fastest way to attach a file in Outlook

To attach a file in Outlook, open a new email or reply, then click the Attach button (usually a paperclip icon) in the toolbar. A file browser window opens — navigate to the file you want, select it, and click Open. The file name appears in the attachment area below the subject line. You can attach multiple files by repeating this step, and you can remove any file by clicking the X next to its name before you send.

The exact location of the Attach button depends on which version of Outlook you use. In Outlook on the web (the version you access through a browser), the paperclip is in the toolbar at the bottom of the compose window. In Outlook desktop (the program installed on your computer), it is in the ribbon near the top. On Outlook mobile apps for iPhone or Android, tap the paperclip icon in the compose area.

Key Takeaways

  • Click the paperclip or Attach button in the compose window, then select your file from the browser that opens.
  • You can attach multiple files to one email by clicking Attach more than once.
  • Most email providers limit file size — Outlook typically allows up to 20 MB per attachment, though your organization may set a lower limit.
  • If a file is too large, Outlook may offer to upload it to OneDrive and send a link instead of attaching it directly.
  • Remove an attachment before sending by clicking the X next to the file name in the attachment area.

Where the Attach button is in different versions of Outlook

Outlook comes in several forms, and the button location changes slightly between them. In Outlook on the web (also called Outlook.com or Outlook 365 accessed through a browser), open a new email and look at the bottom of the compose box — you will see a paperclip icon next to formatting options. Click it to browse your computer for files.

In Outlook desktop (the process you read and install on Windows or Mac), the Attach button is in the ribbon at the top of the compose window. Look for a paperclip icon or the word "Attach" in the Insert tab. Click it and your file browser opens. On Outlook mobile for iPhone or Android, open a new email and tap the paperclip icon — it is usually at the bottom or in the toolbar above the keyboard.

File size limits and what happens when a file is too large

Outlook has a size limit for attachments, though the exact limit depends on your email account type and your organization's settings. Most Outlook accounts allow files up to 20 MB per attachment. If you try to attach a file larger than this, Outlook will either reject the attachment or offer an alternative.

When a file exceeds the limit, Outlook on the web often suggests uploading the file to OneDrive (Microsoft's cloud storage) instead. You authorize the upload, and Outlook sends the recipient a link to read the file from OneDrive rather than attaching it directly. This method works well for large files and lets you control when the recipient can access the file. If your organization uses Outlook desktop, check with your IT department about your specific file size limit, as it may be lower than the standard 20 MB.

Attaching files from cloud storage like OneDrive or SharePoint

You do not have to attach a file from your computer — you can also attach files stored in OneDrive, SharePoint, or other cloud services. In Outlook on the web, click the Attach button and select Browse cloud locations or OneDrive from the menu. Navigate to the file you want and select it. The file is attached as a link, so the recipient can open it directly from the cloud rather than downloading a copy.

In Outlook desktop, the process is similar but the menu option may be labeled differently depending on your version. Look for "Browse Internet Locations" or a cloud icon in the Attach menu. Attaching from cloud storage is useful when the file is very large or when you want to share a file that multiple people are editing — everyone sees the same version rather than multiple copies in different inboxes.

How to remove or replace an attachment before sending

If you attach the wrong file or change your mind about including something, remove it before you send the email. In the attachment area (below the subject line in desktop Outlook, or in the compose box in Outlook on the web), find the file name and click the X next to it. The attachment is removed when ready and does not appear in the sent email.

To replace an attachment, straightforward remove the old one and attach the new file using the Attach button. There is no "replace" function — you remove and re-attach. If you have already sent an email with an attachment and realize you sent the wrong file, you cannot edit the sent email. Outlook does have an "Undo Send" feature in some versions (usually available for a few seconds after you click Send), but it only works if you act when ready.

Attaching files on Outlook mobile apps

The mobile versions of Outlook for iPhone and Android work similarly to the web version, but the interface is smaller. Open a new email or reply, then look for a paperclip icon — it is usually at the bottom of the compose area or in the toolbar. Tap it to open your phone's file browser. Navigate to the file you want (usually in Files, Photos, or Downloads depending on where you saved it) and select it. The file name appears in the attachment area.

Mobile Outlook has the same file size limits as the web version. If a file is too large, the app may suggest uploading to OneDrive instead. You can attach multiple files by tapping the paperclip again, and you can remove any file by tapping the X next to its name before you send.

Common reasons an attachment might not send

Sometimes an email with an attachment fails to send, and the reason is not always obvious. The most common cause is file size — if your total attachments exceed your account's limit, the email will not go through. Check the file sizes and remove any you do not need, or use OneDrive to send large files as links instead.

Another reason is file type restrictions. Some organizations block certain file types (like .exe files or macros in Word documents) for security reasons. If your organization blocks a file type, you will usually see an error message. You can work around this by compressing the file into a .zip folder, uploading it to OneDrive, or asking your IT department whether the file type is allowed. Network problems can also prevent attachments from sending — if your internet connection drops while the email is sending, the attachment may not go through. Try sending again once your connection is stable.

Frequently Asked Questions

Can I attach a folder instead of individual files?

No, Outlook does not allow you to attach a folder directly. You must attach individual files. If you need to send multiple files, attach them one at a time using the Attach button. If you have many files in a folder, compress the folder into a .zip file first, then attach the .zip file — the recipient can unzip it on their end.

What if the recipient says they did not receive my attachment?

First, check that the email actually sent — look in your Sent folder to confirm. If it did send, the attachment may have been blocked by the recipient's email filter or organization. Ask them to check their spam or junk folder. If the file is very large, it may have timed out during sending. Try attaching a smaller file or using OneDrive to send a link instead.

Can I attach a file directly from an email someone sent me?

Yes. Open the email with the attachment you want to forward, then open a new email or reply. In Outlook on the web, you can drag and drop the attachment from the original email into the new one. In Outlook desktop, right-click the attachment and select "Forward as Attachment" or straightforward copy the attachment and paste it into the new email.

Is there a limit to how many files I can attach to one email?

Technically no — you can attach as many files as you want as long as the total size does not exceed your account's limit (usually 20 MB). However, attaching dozens of files makes the email harder to manage. If you need to send many files, consider compressing them into a .zip file or uploading them to OneDrive and sending a link instead.

Why does Outlook sometimes ask to upload to OneDrive instead of attaching?

Outlook detects when a file is large and suggests OneDrive to save space and speed up sending. Uploading to OneDrive and sending a link is faster than attaching a large file directly, and it lets you control permissions — you can decide who can view or edit the file. You can accept the suggestion or click "Attach anyway" to attach the file directly if you prefer.