Email Attachment Size Limits: Gmail, Outlook, iCloud, Yahoo

Most free email services cap a message at 20 to 25 MB: Gmail 25 MB, Outlook.com 25 MB, Yahoo Mail 25 MB, iCloud Mail 20 MB. That limit usually applies to the whole email, and attachments grow by about a third when they're encoded for sending, so in practice you can attach around 18 MB of files to a 25 MB service. For anything larger, send a link instead of an attachment.

Limits by provider (checked on official help pages)

A few details worth knowing:

• Gmail only states a sending limit for personal accounts. For Workspace accounts, both sending and receiving limits are set by the administrator.
• Outlook.com counts everything: text, pictures pasted into the body and attachments. OneDrive links don't count toward the 25 MB.
• iCloud Mail Drop works from Apple Mail on iPhone, iPad and Mac, and from iCloud.com. Attachments can be up to 5 GB, links expire after 30 days, there's a 1 TB Mail Drop storage cap, and the files don't use your iCloud storage.
• The recipient's limit matters too. Your provider may accept 25 MB while the other side rejects anything above 10 or 20 MB. Company mail servers are often stricter than consumer ones.

Why a file under the limit still bounces

Email was designed for text. Attachments are converted into text with Base64, which turns every 3 bytes into 4 characters (RFC 4648). That is a 33% increase before line breaks; RFC 2045 also caps encoded lines at 76 characters, each followed by a line break, which adds a bit more.

So on a 25 MB service, plan for about 18 MB of attachments. On iCloud Mail's 20 MB, plan for about 14 MB. Providers don't all document whether they measure before or after encoding, which is why staying under these numbers is the safe habit.

How to make photos fit

A recent phone photo is often 2 to 6 MB as HEIC or JPEG, and a burst of 8 or 10 of them blows past any limit. Most people opening an email don't need 12 or 48 megapixels.

1. Pick the size you actually need. For viewing on a screen, 2048 pixels on the long side is plenty. For printing at 10×15 cm (4×6 in), about 1800 pixels is enough.
2. Resize first, then compress. Halving the width and height cuts the pixel count to a quarter, which shrinks the file far more than lowering quality alone. Our guide on how to compress an image without losing quality explains the settings.
3. Save as JPEG for photos. JPEG opens everywhere. HEIC and WebP are smaller, but not every recipient's computer opens them; see what a WebP file is if one lands in your inbox.
4. Use the built-in resize options.
   • iPhone (Mail): when you attach large photos, Mail asks to scale them: Small, Medium, Large or Actual Size. Medium or Large is usually right.
   • Mac (Mail): after attaching an image, use the Image Size menu in the message header to choose a smaller size.
   • Windows: select images in File Explorer, right-click and choose Send to > Mail recipient, which offers a picture size if a desktop mail program is set up.
5. Strip metadata while you're at it. GPS location, device model and editing history add a few kilobytes and reveal more than most people mean to share. Our EXIF remover cleans a copy in the browser without uploading it.

When to send a link instead

Attachments are the wrong tool for originals, videos or more than a handful of photos. Use:

• Google Drive from Gmail (it happens automatically above 25 MB).
• OneDrive from Outlook.com (linked files up to 2 GB).
• Mail Drop from Apple Mail or iCloud.com (up to 5 GB, 30-day links).

Remember what a link means: anyone who gets the link may be able to open the file, depending on its sharing settings, and the file now sits on someone's server until you delete it. For personal documents, set the share to specific people and remove it once it's been downloaded. How to share photos privately compares the options.

Common mistakes

• Attaching the original HEIC or RAW. It's large and may not open on the recipient's PC.
• Pasting images into the body. Inline images count toward the limit on Outlook.com, and some mail apps embed them at full size.
• Forgetting video. One minute of 4K video from a phone is easily a few hundred megabytes. Video always needs a link.
• Zipping JPEGs to save space. JPEG is already compressed; a ZIP saves almost nothing. Zip only to bundle many files into one.
• Emailing ID scans and medical photos casually. Email copies sit in your Sent folder, the recipient's inbox and both providers' servers, often for years.

Sensitive photos: think before you attach

Most attachment questions are about vacation photos. Some aren't: a passport scan for a rental, a photo of a prescription, a document for a lawyer. For those, send only what's needed, cropped and with metadata removed, and delete the sent copy once it's no longer needed.

The copies you keep are a separate question. sigil. stores photos and documents in a vault on your phone with 256-bit encryption that only the sign you draw on a 5×5 grid opens. It strips EXIF and location on import and again on export, and it warns you when an export creates an unencrypted copy, which is exactly what an email attachment is. There's no account and no server; it's local-first, with no cloud backup yet. For backups, read how to securely back up private photos.

Bottom line

Plan for about 18 MB of attachments on Gmail, Outlook.com and Yahoo, and about 14 MB on iCloud Mail, because encoding adds a third. Resize photos to around 2048 pixels before sending and you'll rarely hit a limit. For originals, videos or big batches, send a Drive, OneDrive or Mail Drop link, and treat sensitive documents as something to send once and clean up after.

Sources

• Google: Gmail attachment size limits
• Microsoft: Unable to attach files in Outlook.com
• Apple: Mailbox size and message sending limits in iCloud
• Apple: Mail Drop limits
• Yahoo: Message size limits in Yahoo Mail
• IETF RFC 4648: Base64 encoding
• IETF RFC 2045: MIME, line length for Base64