PNG, JPEG, WebP — what each one can and cannot hold

Changing format is not like moving the same picture into a different box. The boxes hold different things, so something is lost the moment it moves. This is about knowing what, before you choose.

What the three formats hold

What each format can carry
Format	Transparency	Compression	Animation
PNG	8-bit, soft edges included	Lossless	APNG only
JPEG	None	Lossy	None
WebP	8-bit	Both lossless and lossy	Yes

The important cell is JPEG’s transparency. JPEG has no alpha channel at all — not a poor one, none. There is nowhere to put it.

Converting something transparent to JPEG

The transparent areas become some colour. The trouble is that most tools pick that colour without asking. Draw onto a canvas and save as JPEG and everything that was transparent comes out black, which is a nasty surprise for anyone expecting white.

This tool asks. White is the default, and choosing the colour the image will actually sit on keeps its edges looking right too.

WebP happens only if the browser can make it

The browser does the encoding. When it cannot produce the format asked for, it does not fail — it quietly returns a PNG. You end up with a PNG that has .webp on the end of its name.

So this tool checks what came back. If it is not what was requested, it says this browser cannot make that format rather than reporting a success. Formats the browser cannot encode are disabled before you can pick them.

A change of format loses the metadata

Converting means decoding the picture and encoding it again, and the original’s Exif, colour profile, and comments do not survive that. Good news for privacy — and it also means the colour profile is gone.

If removing metadata is the actual goal, do not change format. The EXIF viewer and remover lifts the sections out without re-encoding, so the pixels stay exactly as they were. Metadata in photographs has the difference in full.

Animation comes out as one frame

A canvas draws one frame. Feed in an animated WebP or an APNG and the first frame is converted while the rest disappear without comment. This tool recognises those files and says so before converting, rather than explaining afterwards.

If assembling several images into one animation is what you wanted, Images to GIF does that.

So which one

Logos, icons, anything transparent → PNG or WebP. If you need transparency, JPEG is not a candidate.
Photographs for the web → WebP. Smaller than JPEG at the same quality.
Has to open anywhere → JPEG or PNG. The oldest and the most widely handled.
Keeping an original → keep the original. Conversion is one-way, and a lossy format degrades on every save.

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