You recorded a quick screen demo or a birthday message, and now the email client refuses to send it. The math is unforgiving: cameras produce megabytes per second, while email attachment limits sit between 20 and 25 MB on major providers, less in practice once encoding overhead is counted.

Here is how to get a video small enough to email, without making it unwatchable.

Know the actual limits

Gmail, Outlook, and Yahoo all cap attachments around 25 MB per message in practice. Corporate mail servers are often stricter, 10 MB or even 5 MB. And the limit applies to the whole message, so a 24 MB video plus a forwarded thread can still bounce. Target well under the limit: aim for 10 MB or less and you will almost never bounce.

First, question whether email is the right channel

Before compressing: does the recipient need the file itself, or just to watch the video? If watching is enough, upload the video to a sharing platform and send a link instead. A platform like s.pub for short clips transcodes to adaptive streaming, so your recipient watches instantly on any device, at quality that email could never carry. Links also avoid the size lottery of corporate filters entirely.

Email the file only when the recipient needs to keep it, edit it, or play it offline.

The compression settings that work

The efficient path is H.264 with a quality-based rate factor, which spends bits where the eye will notice them:

ffmpeg -i input.mov -c:v libx264 -crf 28 -preset slow -vf "scale=-2:720" -c:a aac -b:a 96k -movflags +faststart output.mp4

What each setting contributes:

CRF 28

For email delivery, where the goal is "clearly watchable," CRF 26 to 28 is the right zone. Going lower inflates the file past what email tolerates; going higher starts to smear text in screen recordings.

Scale to 720p

For demo videos and messages, 720p reads perfectly well on laptops and phones. Halving resolution from 1080p cuts size roughly in half. Keep 1080p only if fine text must stay legible.

Audio at 96 kbps

Voice content sounds fine at 96 kbps stereo, 64 kbps if it is pure talking. Audio is a small share of the file, but every megabyte counts near the limit.

Preset slow

Spends more CPU time for a smaller file at the same quality. For a one-off email video, a few extra minutes of encoding is a fair trade.

Special case: screen recordings

Screen content compresses differently from camera footage. Large flat areas and sharp text mean lower bitrates still look crisp, but fast scrolling or window dragging can smear. If your recording has lots of motion, try CRF 26 first and check text legibility mid-scroll. Also crop dead space around the recording area before encoding: trimming letterboxing and taskbars saves real size and looks more professional.

If it still will not fit

Run the numbers: a five-minute 720p video at email-friendly quality still lands around 25 to 40 MB. Past the limit, your realistic options are trimming the video to the essential minute, dropping to 480p, or switching to a link. For anything meant to impress, like a portfolio piece or a client walkthrough, always prefer the link: full quality, instant playback, no bounce, and no giant file living in someone's inbox forever.

Quick reference

Under 10 MB target for safety, CRF 26 to 28, 720p, AAC 96k, faststart flag, H.264 for compatibility. Over the limit despite all that: trim, or send a streaming link from a video platform instead. The settings get you 90 percent of the way; knowing when to switch to a link gets you the rest.