WebP vs JPG vs PNG: Which Image Format Should You Use?

The same picture can be a 180KB WebP, a 400KB JPG, or a 3MB PNG. Portals, email clients, and older Windows apps do not treat those as interchangeable. Pick the wrong one and you get a rejected upload, a muddy logo, or a file that will not open on a coworker’s PC.

This is a format guide, not a compression lecture. The question is: which container should this picture live in?

The one-sentence rule

• Photos of the real world → JPG (or WebP if the destination supports it)
• Logos, screenshots, text, transparency → PNG
• Modern websites that accept it → WebP for smaller files
• iPhone originals on Windows → convert HEIC to JPG first

JPG (JPEG)

JPG is the universal photo format. Almost every form, CMS, and email client accepts it. It uses lossy compression: it throws away detail you are unlikely to notice in a landscape or portrait.

Use JPG for: camera photos, product shots, blog heroes, email attachments, most government photo fields.

Avoid JPG for: logos, screenshots with small text, anything that needs a transparent background. Each extra save can add more artifacts. If you must edit a photo several times, keep a PNG or original master and export JPG last.

Transparency is not supported. Convert a PNG logo to JPG and the checkerboard becomes a solid color (usually white).

PNG

PNG is lossless for typical 8-bit images and supports a transparent background. File sizes are larger than JPG for photographs.

Use PNG for: logos, icons, screenshots, graphics with sharp edges, cutouts that need transparency.

Avoid PNG for: multi-megapixel phone photos you plan to email. A 12MP PNG can be huge for no visual gain over a high-quality JPG.

If a portal accepts only JPG, convert the PNG and check that a white background is acceptable. Use PNG to JPEG (detailed walkthrough: PNG to JPG converter guide).

WebP

WebP is a newer format from Google. Photos are often much smaller than JPG at similar quality. It can also be lossless and can include transparency, like PNG.

The catch: plenty of desktop apps, older Outlook versions, and official forms still reject .webp. Chrome downloaded a WebP from a website; you try to attach it to a job portal; the portal says “invalid file type.”

Use WebP for: your own website if you control the stack.

Convert WebP with WebP to JPG for photos or WebP to PNG when you need transparency.

Animated WebP becomes a still first frame in most simple converters, including PdfPixels. Do not expect a GIF-like result.

HEIC (the iPhone sibling)

Apple phones often save HEIC. It is efficient on the phone and annoying everywhere else. If Windows Photos or a form cannot open the file, convert it with HEIC to JPG before you do anything else.

A decision table

File-size reality check

Same 12-megapixel phone photo, saved three ways (your numbers will vary, but the pattern holds):

Flip it around for a logo: PNG wins on quality, and the size gap disappears because flat graphics compress efficiently in PNG. This is why the rule is *photos → JPG/WebP, graphics → PNG* rather than "always pick the smallest file."

Why websites serve WebP when forms reject it

Bandwidth. A site serving a million images a month cuts its image traffic roughly in half by switching JPGs to WebP — that is real money on hosting and real speed on mobile. The site controls its own stack, so the "unsupported app" problem never bites. A job portal accepting uploads is the mirror image: it cannot control which ancient viewer a clerk opens files in, so it sticks to JPG and PNG. Same format, opposite constraints, and you are the one stuck converting between them.

What about AVIF?

AVIF is the next-generation format after WebP — smaller still, and already supported in Chrome, Firefox, and Safari. Expect the same pattern as WebP: modern browsers yes, older forms and desktop apps no. The practical advice does not change: keep originals, export AVIF/WebP for sites you control, and keep a JPG handy for everything else.

How to convert without wrecking the picture

1. Start from the original, not a file you already compressed three times.
2. Match the destination. If the portal wants JPG, do not upload WebP and hope.
3. Watch transparency. PNG → JPG fills empty pixels. Preview it.
4. Do not chase tiny files on a logo. Compress a photo; leave a logo as PNG unless you must.
5. One conversion in the UI. PdfPixels convert tools take one image at a time. For a folder of files, repeat or convert the ones the form actually needs.

Quality settings

For JPG output, 85–92% is a sensible default. Going to 40% to hit a KB cap will show banding in skies and skin. If you also have a KB limit, resize the pixel dimensions first, then compress. Format choice and file-size targeting are different jobs — see Compress Image only after the format is right.

Bottom line

JPG for photos. PNG for graphics and transparency. WebP when *you* control the website. Convert HEIC and WebP before they hit a picky form. Start with the converter that matches the destination: WebP to JPG, PNG to JPEG, or HEIC to JPG.