Email was never designed for video. SMTP, the protocol that moves email messages between servers, was built in 1982 for plain text. Attachments were bolted on later using MIME encoding, which converts binary files to Base64 text and inflates their size by roughly 33% in transit. A 25 MB attachment limit on Gmail actually means your original file should be under about 18 MB to survive the encoding overhead reliably.
Why phone videos blow past email limits
A modern smartphone records video at 1080p or 4K resolution using H.264 or H.265 codecs at bitrates between 10 and 50 Mbps depending on the device and quality setting. At 20 Mbps (a common 1080p recording bitrate), one minute of footage produces roughly 150 MB of data. Even a 15-second clip lands around 37 MB before you account for Base64 inflation.
The math is straightforward: to email a video, you need to get it under roughly 18 MB effective size, which usually means reducing both the resolution (pixel dimensions) and the bitrate (data per second).
How resolution affects file size
Resolution has a direct, roughly proportional relationship to file size. A 1920x1080 frame contains 2,073,600 pixels. A 1280x720 frame contains 921,600 pixels, which is 55% fewer pixels. A 640x480 frame has 307,200 pixels, which is 85% fewer than 1080p.
The encoder does not just store raw pixel counts, but the amount of visual information it needs to compress scales roughly with pixel count. Cutting from 1080p to 720p typically reduces file size by 40-55%. Cutting to 480p reduces it by 70-85%.
For email, where the recipient will likely watch the video in a small preview pane on their phone or laptop, 720p is more than sufficient. If the video is a quick clip to show something happened (a package delivery, a quick demo, a funny moment), 480p is perfectly fine and will keep file sizes well under 10 MB for clips under a minute.
Reducing resolution vs. reducing quality
You have two levers to pull: resolution (pixel dimensions) and quality (CRF/bitrate). The best approach for email is to use both.
First, drop the resolution. Going from 1080p to 720p loses very little visual quality at typical viewing sizes. Then, apply moderate compression. A CRF value of 28 for H.264 produces good quality at a fraction of the original file size. Combined, a 60-second 1080p clip that started at 150 MB can easily become a 720p clip under 15 MB with no perceptible quality loss at the sizes people view email attachments.
Email attachment limits by provider
- Gmail: 25 MB (Google recommends Google Drive links for larger files)
- Outlook/Hotmail: 20 MB
- Yahoo Mail: 25 MB
- Apple iCloud Mail: 20 MB for standard attachments, up to 5 GB via Mail Drop
- ProtonMail: 25 MB
- Corporate Exchange servers: Often 10-15 MB, depending on IT policy
If your target is a corporate recipient, assume 10 MB to be safe. For personal email, 20 MB is a reasonable ceiling.
The MediaBrew resize tool handles this in one pass: upload your video, select a resolution preset (1280x720 or 854x480 for email), and download the result. If the resized file is still above the limit, run it through the compress tool with a CRF of 28-32 to shave off more. Processing is local via FFmpeg WebAssembly, so your video never leaves your device.