PNG, JPG, WebP, AVIF — which image format and how to convert between them

Most people pick an image format by accident. You right-click, "Save image as," and whatever it defaults to is what you get. That's fine right up until it isn't — a logo that looks chunky because it got saved as a JPG, a photo that's 8 MB because it's a PNG, a file a website won't accept because it's a HEIC straight off your iPhone. Then you're suddenly in the business of converting formats, usually in a hurry.

The good news: the rules are simple, there are only really four formats that matter, and you never need to upload a private photo to a stranger's server to switch between them. Let's get you sorted.

What each format is actually for

Every format is a different trade between file size, quality, and compatibility. Here's the honest one-liner for each:

Format	Best at	Transparency	Avoid for
JPEG	Photographs	No	Text, logos, sharp edges
PNG	Logos, icons, screenshots	Yes	Photos (huge for no gain)
WebP	Almost everything on the web	Yes	Email, a few old apps
AVIF	Smallest possible files	Yes	Older browsers, fast encoding
HEIC	iPhone storage	Yes	Sharing anywhere but Apple

The reason they differ comes down to how they compress. JPEG throws away detail your eye won't miss — perfect for a sunset, terrible for a screenshot of code where every edge matters. PNG keeps every pixel exactly, which is why it's flawless for a logo and absurdly large for a photograph. WebP and AVIF are the modern formats that do both jobs better, using newer math to hit smaller sizes at the same quality.

That gap is the whole reason WebP took over the web: same picture, a fraction of the bytes, supported in every current browser.

The conversions people actually need

In practice, nobody converts formats for fun. It's almost always one of these five situations:

• HEIC → JPG. Your iPhone shoots HEIC, and half the world's upload forms reject it. JPG is the universal "just accept it already" format.
• PNG → JPG. Someone saved a photo as a PNG and it's 6 MB. JPG drops it to a few hundred KB with no visible difference.
• PNG/JPG → WebP. You're putting images on a website and want pages to load faster. This is the single highest-impact conversion for performance.
• WebP → PNG. You downloaded a WebP and some older program — an email tool, an ancient image editor — refuses to open it.
• Anything → PNG. You need transparency, or a lossless copy with no compression artifacts.

None of these are hard. What they have in common is that the source is often something personal — your photos, a screenshot with a name in it, a document — which is exactly why where the conversion happens matters.

The transparency trap

One thing trips people up constantly: JPEG cannot do transparency. So when you convert a transparent PNG (say, a logo on a see-through background) to JPEG, those transparent areas have to become something — and that something is usually a flat white or black box. If your logo suddenly has an ugly rectangle around it after converting, this is why. Convert to WebP or keep it PNG if you need the transparency to survive.

Rule of thumb for 2026: WebP by default for anything on the web. JPEG when it has to open literally everywhere. PNG when you need transparency or pixel-perfect edges. AVIF when every kilobyte counts and your users are on modern browsers.

Why "in your browser" is the part that matters

Here's the thing the average online converter doesn't advertise: when you upload your photo to convert it, you've handed a company a copy of your photo. For a wedding picture, a passport scan, a screenshot of a private message, that's a strange amount of trust to extend to a website you found ten seconds ago and will never visit again.

Modern browsers can do the entire conversion locally. The file is read, re-encoded, and saved without ever leaving your device — no upload, no server, no copy sitting in someone's logs.

Converting, the private way

Primova's Image Converter runs entirely in your browser. Drop in one image or a hundred, pick the output format, and download — one file, or the whole batch as a single ZIP. The pictures never touch a server.

A couple of practical notes while you're there. Converting to JPEG or WebP gives you a quality slider, so you can trade a little fidelity for a much smaller file. Converting to PNG stays lossless. And if a folder of iPhone HEICs is the problem, you can drop the whole lot in and get usable JPGs back in one go.

One clarification worth making: if your real goal is a smaller file rather than a specific format, the Image Compressor is the better tool — it's built around the quality-versus-size dial and uses the same WebAssembly codecs the Squoosh team built. But when you just need a PNG turned into a JPG, or a pile of HEICs made shareable, the converter does it in a single drag, and nothing you convert ever leaves your machine.