Compress Video for Email
The number to aim for is not the one your email provider advertises. Attachments are base64-encoded before they are sent, which adds about a third, so a 25 MB file meets a 25 MB limit as roughly 33 MB of message and bounces. This page pre-fills 16 MB — the largest size that reliably survives that encoding.
What to know about email
The base64 third
Mail is a text protocol, so a binary attachment is re-expressed as text on the way out: every three bytes become four characters. The limit your provider publishes applies to the encoded message, which puts the real ceiling at roughly the advertised figure divided by 1.37 — about 18 MB for a 25 MB provider.
The strictest server on the route wins
Your provider's limit is only the first one the message meets. Plenty of corporate gateways stop at 10 MB and many providers stop at 20, and the recipient's server has the last word — so a message that left your outbox happily can still be refused at the other end.
Above about 20 MB, send a link instead
Large providers already do this for you, swapping an oversized attachment for a cloud link rather than refusing it outright. If the video matters more than the convenience, uploading it somewhere and sending the URL keeps the quality that any attachment-sized target has to give up.
What fits in 16 MB
| Clip length | Video bitrate | Resolution it picks |
|---|---|---|
| 15 seconds | 8118 kbps | 1920×1080 |
| 30 seconds | 3995 kbps | 1440×810 |
| 1 minute | 1934 kbps | 960×540 |
| 3 minutes | 559 kbps | 480×270 |
| 5 minutes | 284 kbps | 480×270 |
These rows come from the same planner the tool runs, so they are what it would actually choose — not a rule of thumb. Your own clip has its own length, resolution and audio track, and the plan is recomputed against those before anything is encoded. Where a row says the target is out of reach, dropping the audio or trimming the clip changes the arithmetic in your favour; the bitrate calculator does the same sum for a target you type yourself.
Frequently asked questions
Why does this page aim at 16 MB when Gmail says 25 MB?
Because the 25 MB applies to the encoded message rather than to your file. Base64 encoding makes an attachment about a third larger in transit, so a 25 MB video becomes roughly 33 MB of message and is refused. 16 MB encodes to about 21 MB, which fits with room to spare — and still fits at the providers that stop at 20 MB.
What is the largest video I can really attach?
About 18 MB for a provider advertising 25 MB, assuming nothing else on the route is stricter. That is the advertised limit divided by the base64 overhead. Aiming a little under it costs almost nothing in picture quality and removes the risk of a bounce you only find out about later.
Does a smaller attachment send faster?
Noticeably, yes. The attachment is uploaded to your provider before the message goes anywhere, so a 16 MB file is roughly a third of the wait of a 50 MB one on the same connection, and considerably less likely to time out on a slow or mobile link.
Is the video safe to compress here before emailing it?
It never leaves your machine. The compression runs in your browser through WebCodecs, so the file is not uploaded to this site or anywhere else and there is no queue holding a copy of it. That matters more for something you were about to attach to a private message than for most things this tool gets used for.