How to send large files by email

You cannot email a large file, and the limit is lower than the number your provider advertises. Most mail services cap attachments at around 25 MB, but attachments are encoded roughly 33% larger than the file on disk — so treat 20 MB as the real ceiling. Above that you send a link instead, and there are four ways to do it.

Why the limit exists and why it has not moved

Email attachments are encoded into text before sending, using a scheme that inflates the file by about a third. That encoding is part of how email has worked since the early 1990s, and mail servers all along the delivery path enforce their own size limits — including the recipient's, which you cannot see.

That is the key point people miss: your provider's limit is not the only one that applies. A 20 MB attachment can be accepted by your server and bounced by theirs. The whole chain has to agree, so a large attachment is unreliable even when it is technically under your cap.

~20 MB

Common caps: Gmail 25 MB, Outlook 20 MB by default for some configurations, many corporate mail servers 10 MB. If you do not know the recipient's, assume 10 MB.

The four ways to send it anyway

1. A transfer service link

Upload the file, get a link, paste the link into the email. This is the most reliable option because the email itself is tiny — nothing in the delivery chain can reject it.

It also decouples the file from the message, which is quietly valuable: you can revoke the link later, set an expiry, or add a password. An attachment, once sent, is gone and lives in the recipient's mailbox forever.

Any of them will do for a file that was merely too big to attach. The free ceilings run from 2 GB up to SwissTransfer's 50 GB, and unless your file is genuinely enormous, pick on what the recipient sees rather than on size — some free tiers put advertising on the download page you just sent a client to. The fuller comparison has each figure and the date it was checked.

2. Your provider's built-in cloud handoff

Gmail offers Google Drive, Outlook offers OneDrive. Attach something too large and it converts the attachment into a link automatically.

Convenient, and it has a catch worth understanding: it shares a file out of your storage rather than handing over a copy. The recipient's access is a permission against your Drive, so if you later move, rename or reorganise that file, you have changed what their link does. And depending on your organisation's settings they may hit a sign-in wall.

The Gmail version of this and the fuller Drive argument go into it properly.

3. Compress it

Sometimes the file is only just too big and zipping gets you under. Zipping is lossless, so nothing is damaged.

Be realistic about what compresses. Text, spreadsheets and uncompressed image formats shrink usefully. Video, JPEG, MP3 and PDF are already compressed and will shrink by a few percent at best — if you zip a 40 MB video expecting it to fit under 25 MB, it will not.

Do not re-encode a video or export images at lower quality to fit an email limit. That damages a deliverable to avoid using a link. Compression is a decision about a preview, not about the real file.

4. Split it into parts

Archive tools can split a large archive into fixed-size volumes. It works, and it is almost always the wrong answer: the recipient needs the same tool and all the parts, and losing one makes the rest useless. Consider it only when a link genuinely cannot be used — some locked-down corporate environments block transfer services outright.

The rule, by size

Under 10 MB: attach it. It will be fine.

10–20 MB: attach it if you know the recipient's mail system, send a link if you do not. A bounced 18 MB attachment costs you a round trip and looks careless.

Over 20 MB: send a link. Every time.

Anything with other people's personal data in it: send a link with an expiry, and consider a password sent through a different channel. An attachment sits in a mailbox indefinitely, gets forwarded, and is backed up by systems you have no visibility into — which is precisely the problem with emailing anything sensitive. How to send confidential documents covers it properly.

Two habits worth having

Say what the link is. "Here's the file" plus a bare URL reads like phishing, and increasingly gets filtered like it too. Name the file, say roughly how big it is and when the link expires.

Never put the password in the same email as the link. If the mailbox is compromised or the message is forwarded, the password protected nothing. Send it by text or say it on a call. This costs ten seconds and is skipped constantly.

If you are doing this weekly

The pattern to notice is re-uploading the same files because a link expired. That is the point at which a free transfer tier is costing you more time than a plan would cost you money — and expired links are the most common version of it.