Why Your File Is Too Large to Email (and How to Actually Send It)

By Andrew Butson · July 2, 2026 · 7 min read

You attach a video, or a handful of photos, and hit send. The message either bounces back with "attachment too large" or just hangs on "sending…" forever. The file isn't broken and neither is your email; it's simply bigger than what mail servers were ever built to carry in one piece.

Every major provider caps attachments somewhere between 20 and 25 MB, and that number is smaller in practice than it looks. Here's what's actually going on, and the fixes that work depending on how much smaller the file needs to get.

Why email has a size limit at all

Email attachments aren't sent as raw bytes. They're base64-encoded so they can travel safely inside a text-based message format, and base64 turns every 3 bytes of the original file into 4 bytes of encoded text. That's roughly a third more data than the file itself, which means a provider's "25 MB limit" leaves real room for closer to 18–19 MB of actual file content once encoding overhead is accounted for. On top of that, mail servers have to accept, store and relay the entire message as one atomic unit, and there's no resuming a failed send partway through, so providers keep the ceiling low to protect mailbox storage and delivery reliability for everyone, not just you.

The specific ceiling depends on which provider is sending and which is receiving, and the smaller of the two always wins: Gmail allows up to 25 MB per message, Yahoo Mail 25 MB, and Outlook.com 20 MB (a Microsoft 365 organisation account can be configured up to 150 MB by an administrator, but that isn't the default). Send a 22 MB file from Gmail to someone on Outlook.com and it can still bounce at their end even though it cleared yours.

Shrinking the file before you send it

What actually helps depends on what kind of file it is:

• Photos: a screenshot or photo saved as PNG or HEIC can run 8–15 MB; converting it to JPEG at a sensible quality setting typically brings that down to a fraction of the size with no visible difference in an email attachment. Several large photos together add up fast even when each one looks small on its own.
• Video: this is the usual culprit. A couple of minutes of 4K footage from a phone can easily run several hundred megabytes, and reports based on Apple's own specs put ProRes recording on iPhone at roughly 6 GB per minute at 4K. Re-encoding to a standard, more efficient MP4 shrinks a typical phone video substantially, though a clip that's already been through an efficient codec won't shrink much further.
• Zipping a folder: worth doing for a batch of documents, spreadsheets or text files, which compress well. It does almost nothing for photos or video, since JPEG and MP4 are already compressed, so zipping a file that's already compressed rarely saves more than a percent or two.
• Splitting into several emails: a last resort if there's genuinely no cloud option available to you, and clumsy enough that it's rarely worth it once the alternative below exists.

Sending a link instead of an attachment

Past a certain size, a link beats an attachment outright. Gmail and Outlook both detect when a file is too large to attach directly and offer to upload it to Google Drive or OneDrive instead, dropping a shareable link into the email in place of the file, so the recipient clicks through rather than downloading an attachment. It's the most reliable option for anything that won't realistically shrink below the limit, like a long video or a large batch of raw photos, at the honest cost of the file now sitting on that cloud provider's servers rather than staying strictly between sender and recipient.

Where converting locally fits

For files that are oversized because of their format rather than their content, such as a HEIC photo, an uncompressed WAV recording, or an old MOV straight off a camera, converting to a more efficient format first is worth doing before you reach for a cloud link. It's the one part of this that Morphr genuinely helps with: the conversion happens in your browser, so the file being shrunk never has to leave your device just to do it. Being straightforward about the limits, though: Morphr doesn't currently have a "compress to exactly 20 MB" target-size option, so a very large or already-efficiently-compressed video may still end up over the limit after conversion. In that case the honest answer is a shared link, not a smaller file; no amount of re-encoding gets a genuinely long video under 20 MB without visibly hurting it.

Frequently asked questions

Why is my one-minute video so much bigger than a whole folder of photos?

Video is dozens of full frames every second rather than one image, and phones increasingly record at high resolution and bitrate by default. Reports based on Apple's own specs put ProRes recording alone at roughly 6 GB per minute at 4K; even standard H.264/HEVC recording commonly runs into hundreds of megabytes for a minute or two, which clears a 20–25 MB email limit many times over.

Does zipping a file actually make it smaller?

For documents, spreadsheets and text files, usually yes, and often significantly. For photos and video, barely: JPEG and MP4 are already compressed formats, so wrapping them in a zip file rarely saves more than a percent or two.

Why did Gmail turn my attachment into a Google Drive link on its own?

Gmail automatically uploads anything over its attachment limit to Google Drive and inserts a link in the message instead of blocking the send outright. The recipient needs the link to be accessible to them, set to "anyone with the link" if they don't have a Google account, or they won't be able to open it.

Will converting a file to shrink it lose quality?

It depends on the target: converting an uncompressed format like BMP or WAV to something like PNG or FLAC can shrink the file with zero quality loss, because the target is still lossless. Converting a photo or video to a lossy format like JPEG or a re-encoded MP4 does trade some quality for size, though at a sensible setting it's rarely noticeable in something you're emailing.