.webp images don't render in classic email clients

Great for the web, ignored by Outlook

I run a strict rule across my own systems: every image gets converted to .webp the moment it's uploaded. Any JPEG, flat PNG, or PNG with an alpha channel gets converted before it goes anywhere. It's automated across my whole content pipeline, so the file on disk, the site serving it, and what the software expects always agree. It's a good rule, and it's caught real problems.

It ran into a case it wasn't built for: an email needed a logo, and the format my "always convert" rule produces doesn't render reliably in classic email clients.

Why the exception is real

Outlook's desktop app renders HTML email through Word's engine, not a browser engine, and it has never added .webp support -- caniemail.com's own tracked support table shows it unsupported across every desktop Outlook version, alongside several other older or corporate mail clients. The image isn't corrupted and the markup isn't wrong -- the client just doesn't know the format, so the reader gets a broken-image icon where the logo should be.

There's no fix on the .webp side of this. If an image is going into an email rather than onto a web page, it needs to stay (or get a fallback copy) in a format email clients actually decode -- PNG or JPEG -- and an automated "convert everything to .webp" pipeline needs to know the difference between the two destinations before it touches the file.