The short answer
Use JPG for photos when universal compatibility matters, PNG for transparency and sharp UI assets, WebP for most modern web images, AVIF when maximum compression is worth testing, GIF for simple legacy animation, and SVG for logos or icons that need to scale.
The best format depends on the destination. A product photo, app icon, scanned receipt, transparent logo, and animated sticker all need different conversion decisions.
When to convert images
Convert PNG to JPG when transparency is not needed and file size matters. Convert JPG to WebP when you want lighter product images or blog images. Convert AVIF to JPG when an older app cannot open a modern AVIF file.
Keep a high-quality original when possible, then export the smallest format that still looks clean in the place where the image will be used.
Best settings for website images
For hero photos and product images, start with JPG or WebP and compare visual quality at the final display size. For transparent logos, icons, and UI screenshots, keep PNG or WebP so edges stay clean.
If you are optimizing for SEO and Core Web Vitals, do not only chase the newest format. Use the format that keeps the page light while still rendering correctly in the browsers, CMS tools, and social previews your audience uses.
Common format mistakes
Do not use PNG for every product photo just because it sounds higher quality; the files can be much larger. Do not use JPG for transparent artwork; it will flatten the background. Do not rely on AVIF everywhere unless your workflow has a JPG or WebP fallback.
Quality checklist
Check transparency, text sharpness, color banding, and file size after conversion. For UI screenshots and graphics with text, PNG or WebP usually holds edges better than heavy JPG compression.
For SEO and page speed, the winning image is not the newest format by default. It is the smallest file that still renders correctly for the users and browsers you care about.