Compress a video to 25 MB

Who stops at 25 MB, and what they count

Several big email services share the 25 MB figure, but they do not all add up the same parts of a message:

Each limit links to the service's own help page. Work and school Gmail accounts have limits their administrator sets, and so do Exchange mailboxes, where classic Outlook's default is 10 MB (see compress a video to 10 MB).

How much video fits in 25 MB

The longer the video, the fewer bits each second gets, so Auto lowers the picture size as the length grows. For a 1080p phone video at 30 frames per second with AAC sound, this is what you get:

Every row clears Auto's bar of about 0.05 bits per pixel in each frame, the point where a phone video still looks clean, except the last. A 4K video keeps 4K for about 15 seconds and 1440p up to about 30; from 45 seconds on it gets the same picture as a 1080p one. Past about 20 minutes with sound, 25 MB turns blocky, and the panel warns you before you start.

Aim under 25 when the email carries more

Outlook.com counts the words of the email and any picture placed in it as part of its 25 MB, and Gmail and Yahoo Mail add up every attachment. A video made to exactly 25 MB leaves no room for anything else, so tap 23 MB if you will add a signature image, a document or a long message.

Proton Mail warns that encoding makes attachments a bit larger than the files on your device. If it turns down a 25 MB video, compress the video again at 23 or 20 MB.

Classic Outlook for Windows has its own 20 MB default for IMAP and POP accounts, such as a Gmail address added to Outlook, whatever the email service itself allows. Its error says "The file you're attaching is bigger than the server allows" (Microsoft Learn). Choose 20 MB there.

4K, 60 fps and vertical phone videos

Phones record in 4K and at 60 frames per second, and that fills 25 MB within seconds. Auto copes with both: it tries 30 fps before it shrinks the picture, and it never makes a picture bigger than the original. A minute of 4K at 60 fps comes out at 720p, still at 60 fps; at a minute and a half it becomes 720p at 30 fps. In our tests, 10 seconds of 4K came out at 24.2 MB, still 3840 x 2160, in about 14 seconds.

Vertical videos keep their shape. A 1080 x 1920 phone video becomes 720 x 1280 at one minute, upright, with no black bars added at the sides.

iPhones can record in HEVC, the High Efficiency format (Apple). Such a video compresses here only where your browser can decode HEVC, and the tool checks that before anything starts. The 25 MB copy is always H.264 in an MP4.

Over 25 MB: share a link or split it

When the video has to stay long and sharp, a link works better than an attachment. Gmail moves attachments over its limit to Google Drive on its own (Gmail Help), and Outlook.com can attach a OneDrive file of up to 2 GB as a link, which does not count toward its 25 MB (Microsoft).

To keep it as an attachment, split the video into parts with the cut video tool, then compress each part to 25 MB here and send one email per part. Each part gets the full 25 MB, so a 4-minute video sent as two halves stays at 720p, where in one piece it would be 480p.