The fastest way to attach a file in Outlook

To attach a file in Outlook, click the Attach button in the message compose window, then select the file from your computer. On Windows, the Attach button is in the toolbar at the top of a new email. On Mac, it's in the Message menu or the toolbar, depending on your Outlook version. The file uploads to your message immediately, and you can attach multiple files at once by selecting them together.

If you don't see an Attach button, you may be using Outlook Web (the browser version). In that case, click the paperclip icon near the bottom of the compose box. The process is the same: select your file, and it attaches to the message.

File size limits exist in most Outlook setups. Outlook.com and Microsoft 365 allow attachments up to 25 MB each. If your organization uses an on-premises Exchange server, the limit may be different — ask your IT department if you're unsure. If a file is too large, you can compress it, split it into parts, or use OneDrive to share it instead.

Key Takeaways

  • Click Attach (Windows) or use the paperclip icon (web version) to add files to an email.
  • You can attach multiple files at once by selecting them together in the file browser.
  • Most Outlook accounts limit attachments to 25 MB per file, though your organization may have different limits.
  • If a file is too large, compress it first or use OneDrive to share the link instead of attaching the file itself.
  • On Mac, the Attach button location varies by Outlook version — check the Message menu if you don't see it in the toolbar.

Where to find the Attach button in different Outlook versions

In Outlook for Windows (2016, 2019, and Microsoft 365), the Attach button sits in the toolbar of the compose window, usually near the Format Text options. It looks like a paperclip. Click it once, and a file browser opens so you can navigate to the file you want.

In Outlook for Mac, the location depends on your version. In newer versions (2016 and later), look for the paperclip icon in the toolbar at the top of the compose window. In older versions, go to the Message menu and select Attach File. If you're not sure which version you have, click Outlook in the menu bar, then About Outlook.

In Outlook Web (Outlook.com or your organization's web-based Outlook), open a new message and look for the paperclip icon near the bottom of the compose box, usually to the left of the Send button. Click it to open the file browser.

Attaching files from OneDrive or SharePoint instead of uploading

Instead of attaching a file directly, you can share a link to a file stored in OneDrive or SharePoint. This is useful for large files or when multiple people need to edit the same document. In Outlook for Windows and Mac, click Attach and look for an option like Browse Cloud Locations or OneDrive. Select the file, and Outlook inserts a link rather than uploading the file itself.

In Outlook Web, click the paperclip icon and select Browse Cloud Locations. You can then navigate to OneDrive or SharePoint and choose the file. The recipient gets a link they can click to view or download the file, and you can control permissions — for example, allowing them to view only, or to edit.

Sharing a link is faster than uploading a large file, and it keeps everyone working from the same version. The downside is that the recipient needs access to OneDrive or SharePoint to open the link, so check with them first if they're outside your organization.

What happens if your attachment is too large

If you try to attach a file larger than 25 MB in Outlook.com or Microsoft 365, Outlook will warn you before you send. You have a few options: compress the file, split it into smaller parts, or use OneDrive instead.

To compress a file on Windows, right-click it, select Send to, then Compressed (zipped) folder. On Mac, right-click the file and select Compress. The compressed version is usually 50 to 80 percent smaller, though it depends on the file type. After compressing, try attaching it again.

If compressing doesn't help, upload the file to OneDrive, right-click it, select Share, and copy the link. Paste the link into your email instead of attaching the file. This works for any file size and lets the recipient download it directly from OneDrive.

Attaching multiple files at once

You don't have to attach files one at a time. When the file browser opens after you click Attach, hold Ctrl (Windows) or Cmd (Mac) and click each file you want to attach. All selected files will attach to the message at once.

If the files are in the same folder and you want to attach most of them, you can also select all files with Ctrl+A (Windows) or Cmd+A (Mac), then deselect the ones you don't need by holding Ctrl or Cmd and clicking them again.

Removing or replacing an attachment

After you attach a file, it appears in the compose window below the message body. To remove it, hover over the attachment and click the X button that appears. The file is removed from the message but stays on your computer.

To replace an attachment, remove the old one first, then attach the new file. There's no direct "replace" option in Outlook, so this two-step process is the standard way.

Frequently Asked Questions

Can I attach files from my phone or tablet?

Yes, but the process depends on which app you use. In Outlook for iOS or Android, open a new message, tap the paperclip icon, and select a file from your device or cloud storage. You can attach photos, documents, and other files the same way you would on a computer.

What file types can I attach?

Outlook accepts almost any file type — documents, spreadsheets, images, videos, and more. However, some organizations block certain file types for security reasons, such as .exe or .zip files. If your attachment is blocked, your IT department can tell you why and whether you can send it a different way.

Does the recipient need special software to open my attachment?

It depends on the file type. If you attach a .docx file, the recipient needs Microsoft Word or a compatible program like Google Docs. If you're unsure what software they have, ask them first, or convert the file to a more universal format like .pdf before sending.

Can I attach a file that's currently open in another program?

Yes. Outlook doesn't lock files while you're composing a message. You can attach a file even if it's open in Word, Excel, or another program. However, if you make changes to the file after attaching it, those changes won't be included in the attachment — the version that was on disk at the time you attached it is what gets sent.

Why does my attachment show as a link instead of a file?

This usually means Outlook automatically converted it to a OneDrive link. This happens when you attach a file from OneDrive or when your organization has policies that encourage cloud sharing. The recipient can still download the file by clicking the link — it's not a problem, just a different way of sending it.