How to Send a File Too Big for Email

The message bounces, or the send button just sits there. Somewhere a limit was crossed, and the usual reflex — right-click, compress to zip — does almost nothing. Here is why, and what actually works, in the order worth trying.

Your 24 MB file is bigger than 24 MB

Email cannot carry raw binary. Attachments are encoded into plain text before they travel, and the standard encoding turns every three bytes into four characters. That is roughly 33% overhead, plus a little for headers and boundaries.

So a 24 MB file arrives at the server as about 32 MB of message, and a 25 MB limit rejects it. The practical ceiling for a 25 MB mailbox is closer to 18 MB of actual file. That single fact explains most of the "but it is under the limit" confusion.

The common limits, for orientation:

Service	Limit per message
Gmail	25 MB
Microsoft 365 / Outlook.com	25 MB by default, administrators can raise it
iCloud Mail	20 MB

And the one that catches people out: the smaller of the two limits wins. Your 100 MB corporate allowance is irrelevant if the recipient is on a 20 MB plan. You will not get a useful error message about it either — the bounce arrives hours later, if at all.

Why zipping almost never helps

Zip compression looks for repetition. It is very good at that, which is why a folder of spreadsheets, CSV exports or source code can shrink by 80%.

But JPEG, PNG, WebP, MP4, MP3 and PDF are already compressed. The repetition has been squeezed out of them once. Running zip over a JPEG typically saves one or two percent, and occasionally makes the file slightly larger because of the archive's own bookkeeping.

Zip is worth it when: many small files, mostly text, and you want them to arrive as one item. It is not worth it when: one photo, one video, one scanned PDF.

Option 1: make the file genuinely smaller

This is the only option that leaves you with a real attachment, and for images it is usually enough.

• Photos. A phone photo is 4 to 12 MB and roughly 4000 pixels wide. For anything that will be looked at on a screen, half that width and 75% quality is indistinguishable and a fraction of the size. The image compressor shows the before and after side by side at full zoom, so you can see what you are giving up rather than guessing.
• Format. Converting a PNG screenshot to JPEG or WebP often cuts it by 70%, because PNG is lossless and stores every pixel exactly. The image converter handles that in one step. Keep PNG only when you need transparency or crisp text at small sizes.
• PDFs of scans. These are large because each page is a photograph. Reducing the resolution of the source images before you build the PDF is the effective move; see how to compress images for the numbers.

Option 2: send only the part they asked for

Often nobody wanted the whole thing. One signature page out of a forty-page contract, chapter three out of a manual, the two photos that matter out of sixty.

Split PDF pulls out a page range as its own file, which usually takes the problem below the limit and — more importantly — saves the recipient from scrolling. It is the option people skip because it requires deciding what actually matters.

Option 3: send a link

Cloud storage, a file-transfer service, or the "attach from Drive" button your mail client offers when you cross the limit.

This works for large files and is the only realistic answer for video. It comes with three costs that are worth naming:

• The link is not a copy. Move, rename or delete the file and the recipient's link dies — possibly months later, when they go back to it.
• Access control is easy to get wrong. "Anyone with the link" means anyone the link is forwarded to. For anything with names, addresses or bank details, that is a real exposure.
• Links from strangers look like phishing, because that is exactly what phishing looks like. For a job application or an invoice to a new client, a small attachment lands better than a download link.

Option 4: split the file itself

Multi-part archives (.z01, .zip.002) and "send in three parts" exist. They work, and they are the last resort, because the recipient now needs the same tool, all the parts, and the patience to reassemble them. Expect at least one round of "part 2 did not arrive".

What to do, in order

1. Check the real numbers: file size, your limit, their limit, plus a third for encoding.
2. Try to make the file smaller — recompress the images, change the format, drop the resolution to what the screen actually needs.
3. Send only the pages or files that were asked for.
4. If it is still too big, send a link — and say in the message how long it will stay up.
5. Split the archive only when nothing else is possible.

The first three keep the file in the message, where it stays findable in the thread years later. That is worth more than it sounds: a link expires, a mailbox does not.

Both tools above run entirely in your browser. Nothing is uploaded, which matters most in exactly the situation this article is about — the file was too big to send, so it is probably not a small unimportant one.