Compression guide

How to compress video for Outlook / Office 365

Outlook's default attachment limit is 35 MB for personal accounts. Business tiers raise it to 150 MB. Many corporate IT setups override this lower (10-20 MB) — when in doubt, target 23 MB to match the Gmail floor.

Size limit

35 MB

Target output: 33 MB (with safety margin)

Outlook.com personal: 35 MB

Microsoft 365 Business: 150 MB

Enterprise (admin configurable): 150 MB

Recommended settings

Codec	H.264
CRF (quality)	27
Audio bitrate	96 Kbps AAC
QuickVid mode	Tiny

ffmpeg one-liner

For terminal-comfortable users, here's the exact command:

ffmpeg -i input.mp4 -c:v libx264 -crf 27 -preset medium -vf scale=-2:720 -c:a aac -b:a 96k output.mp4

Install ffmpeg via Homebrew: brew install ffmpeg

Tips

•Office 365 admins frequently set lower limits than the platform default — confirm with IT before assuming 35 MB
•Outlook for Windows and Outlook for Mac handle attachments slightly differently — the size limit is the same but encoding behavior varies
•OneDrive integration suggests itself when files exceed limit; that bypasses size constraints with a shared link

Skip the terminal

QuickVid Compress wraps these settings into a one-click "Tiny" mode. Drop your video, pick the mode, save the result. About 30 seconds end-to-end.

Try QuickVid

Frequently asked questions

What is the video size limit for Outlook / Office 365?

Outlook / Office 365's default video size limit is 35 MB. Outlook.com personal: 35 MB; Microsoft 365 Business: 150 MB; Enterprise (admin configurable): 150 MB. To fit comfortably below the limit, target 33 MB when compressing.

What's the best codec for Outlook / Office 365?

H.264 at CRF 27 produces the best balance of size and quality for Outlook / Office 365. 96 Kbps AAC audio is the right pairing — universal compatibility and small footprint.

How do I compress a video for Outlook / Office 365 on Mac?

Drop the file into a Mac compressor like QuickVid Compress (use the "Tiny" mode) or run the ffmpeg one-liner: ffmpeg -i input.mp4 -c:v libx264 -crf 27 -preset medium -vf scale=-2:720 -c:a aac -b:a 96k output.mp4. Both produce output that fits Outlook / Office 365's 35 MB limit with no visible quality loss.

Why does Outlook / Office 365 reject my video?

Most rejections are file-size related: Outlook / Office 365 caps at 35 MB. Other reasons include unsupported codec (use H.264 for maximum compatibility, not HEVC), missing the +faststart flag (which keeps streaming usable on slow connections), or audio in a non-AAC container.

Can I send larger videos via Outlook / Office 365?

Outlook / Office 365 offers higher limits on paid tiers — Enterprise (admin configurable) accepts 150 MB. Alternatively, host the video elsewhere (YouTube unlisted, Google Drive, Dropbox) and share a link. For sensitive content where you don't want third-party hosting, compress aggressively to fit the free tier.