Compress a video so it fits a Gmail or Outlook attachment

If a client, a school, or a hiring panel wants the video in the message, keep the original and make a smaller MP4. Gmail personal accounts allow about 25 MB of attachments; over that, Gmail can insert a Drive link. Outlook.com and internet accounts use a 20 MB message size, and that figure includes the attachment and the message. Exchange’s default is 10 MB, and an administrator can change it. Aim under the cap you actually have.

Different mailboxes and company servers can use other caps. Ask if you are sending to a company domain.

What the major consumer services actually do

Gmail figures below were checked on 21 September 2026. Outlook figures were checked on 12 October 2026. Enterprise and self-hosted mail can differ, and administrators can lower or raise caps.

Sources: Gmail attachment help; Workspace attachment size; Microsoft: reduce attachment size with Outlook (Outlook.com 20 MB message size and Exchange default 10 MB, checked 12 October 2026); Yahoo message size limits; Apple Mail Drop limits. Yahoo and iCloud rows were not re-checked on 12 October 2026.

Why a 24.9 MB file can still bounce

Some systems measure the file you attached. Others measure the encoded message on the wire. MIME/Base64 can make a binary attachment larger in transit than it looks on disk. Headers and a HTML signature add a little more. If the receiving server is stricter than the sending app, the bounce talks about the message, not the MP4 you exported.

A working habit: aim a few megabytes under the limit you actually know. For Gmail, a sharing copy around 18–24 MB leaves room under 25 MB. For Outlook.com, the 20 MB cap is the whole message, so the file itself needs to land lower than 20 MB.

Attachment, Drive link, Mail Drop — different jobs

• Direct attachment stays in the thread. Useful when the other side will not or cannot open an external file-share domain.
• Google Drive / OneDrive is what the webmail product itself often prefers above its attachment cap. Recipients may need access, and the file is no longer “just sitting in mail.”
• Mail Drop expires (Apple: 30 days). Fine for a quick hand-off; weak as an archive.

None of those outcomes is automatically a privacy disaster. Uploading an unreleased cut to an unknown “free compressor” site is a different risk: you add a copy you do not control. Compressing in the browser avoids that extra hop. It does not make the email itself confidential.

Estimate bitrate from duration

File size is mostly bitrate × duration, plus audio. Resolution only helps the picture look acceptable at a lower bitrate. These numbers are starting points for an H.264 AAC copy aimed at a ~20 MB file, not a guarantee:

Talking-head audio rarely needs 256 kbps. 96–128 kbps AAC is usually enough and leaves more of the budget for the picture. Keep the camera original; export a copy.

One local encode against the 25 MB line, 29 October 2026

On 29 October 2026 Gmail Help still said: “For personal Gmail accounts, the limit is 25 MB.” The same page said to use Google Drive for large files over the size limit, such as videos, and that a Workspace administrator sets work and school attachment limits. The page does not define MB as 1,000,000 bytes or as 1,048,576 bytes. The two products below are arithmetic on this file, not a reading of Gmail’s unit.

ffmpeg 6.1.1-3ubuntu5 wrote a 12.000000 second 1280×720 test pattern with temporal noise and a 440 Hz tone. The source command used libx264 ultrafast at 25000k video, minrate 22000k, maxrate 25000k, bufsize 25000k, and AAC at 160k. The output command used libx264 medium at 800k video, maxrate 800k, bufsize 1600k, AAC at 96k, and +faststart. The compress control on the email tool was not used.

The output is smaller: 38452098 bytes in, 567974 bytes out. ffprobe duration on the output is 12.010000 seconds. The wrapped Base64 body of the output, 76 columns and CRLF, is 777230 bytes, under both 25,000,000 and 26,214,400 before message headers. The source file and its wrapped body are above both. The record is docs/evidence/runs/2026-10-29-comp-fixtures.json.

Before you hit send

1. Keep the master. Never overwrite the recording you might still need.
2. Compress locally. Compress a video for email (Gmail 25 MB or Outlook 20 MB) re-encodes in the browser. The Outlook preset is aimed at the 20 MB message size. Export the sharing copy, then check the downloaded file before attaching it. A local target is not a promise the mailbox will accept the message.
3. Look at the downloaded file size in the finder/explorer, not only the encoder’s estimate.
4. If the other side is a company mailbox, ask what their cap is. Do not assume Gmail’s 25 MB.
5. If a link is acceptable, use the provider’s own Drive / OneDrive / Mail Drop path instead of inventing a third-party transfer.

The compressor page still loads its own scripts from this site. The source video does not have to be uploaded to our server for transcoding. The page itself still loads its code from this site; the Network panel lets you verify that the video bytes are not sent away during the encode.