Your site vs their form: JPG and WebP
Stop picking one winner. Pick the audience — visitor browser or third-party validator.
Most "JPG vs WebP" articles pretend one format wins everywhere. Real work splits in two: assets you ship on a domain you control, and files you push into someone else's upload widget.
Audience A: pages you own
You can serve WebP (often with JPG fallback) and measure Core Web Vitals. Smaller hero images help LCP when your CDN and HTML cooperate. Try convert to WebP and compress to a KB band that matches your design system.
Audience B: portals you do not control
Government, exam, and HR systems publish allow-lists — frequently JPG or PDF only. Uploading WebP because it is smaller on your blog does not help if the validator rejects the MIME type. Default to JPG unless the instructions name WebP explicitly.
Decision in one sentence
WebP for performance you measure; JPG for compliance you cannot negotiate.
Need both from the same master file? Convert once per destination — or run HEIC/PNG → JPG for the form and PNG → WebP for the site as separate exports rather than re-compressing the same JPG three times. See why repeated JPG saves hurt quality.