If you've ever wondered why one photo loads instantly while another one spins forever, the answer is almost always the file format. Picking the right image format is one of those small decisions that makes a surprisingly big difference, whether you're running a blog, an online store, or just sending photos to a client. This guide breaks down each major format in plain language, without the technical jargon.
JPG: the format most photos should use
JPG has been around since the 1990s and it's still the right choice for most ordinary photographs on the internet. It works by throwing away some picture information that your eyes barely notice, which is why the files are so much smaller than other formats. The quality setting controls how much gets thrown away. Somewhere between 75 and 85 out of 100 is the sweet spot where files are small but photos still look sharp. Go above 90 and the file size balloons without any visible improvement. Go below 60 and you'll start noticing blocky patches in skies and smudged details in faces.
JPG is a poor choice for anything that isn't a photograph. Logos, text screenshots, and diagrams with sharp edges come out looking fuzzy and smudged because JPG compression struggles with flat colors and hard lines.
PNG: for graphics and transparency, not photos
PNG keeps every single pixel exactly as it was, with no quality loss at all. It also supports transparent backgrounds, which JPG cannot do. This makes PNG the correct format for logos, app icons, screenshots with text, and any image you've removed the background from. The downside is file size. A PNG photo can be five to ten times larger than the same photo saved as JPG, with no visible quality difference to a normal viewer. A lot of people assume PNG means better quality across the board, but for real photographs it just means a much heavier file for no benefit.
WebP: a solid middle ground for the modern web
WebP was created by Google specifically to replace both JPG and PNG for websites. It can compress photos nearly as well as JPG while also supporting transparency like PNG. Files are typically 25 to 35 percent smaller than the equivalent JPG at the same visual quality. Every browser released in the last several years supports it without any problem, so if you're building or updating a website today, WebP is usually the best default choice for images.
The one situation where WebP causes trouble is sharing files with someone using older desktop software, since a handful of older Windows photo viewers still can't open it properly. For general web use though, it's hard to beat.
AVIF: even smaller, but still catching up
AVIF is the newest format on this list and compresses even better than WebP, often producing files 30 to 50 percent smaller at similar quality. The tradeoff is that creating an AVIF file takes more processing time, and some older image editing software still can't open it. If you run a website with heavy traffic and want to shave every possible kilobyte off your images, AVIF is worth the extra effort. For everyday use, WebP is simpler and nearly as good.
HEIC: great on iPhone, a headache everywhere else
If you own an iPhone, every photo you take is automatically saved as HEIC. Apple uses this format because it stores high quality images in roughly half the file size of JPG. The problem shows up the moment you try to upload that photo to a website, attach it to an email for someone using Windows, or open it in most non-Apple photo software. Many of these will simply reject the file or show an error. The fix is always the same: convert the HEIC file to JPG before sending it anywhere outside the Apple ecosystem.
A quick cheat sheet
Use JPG for regular photos you're sharing, emailing, or uploading to most websites. Use PNG when you need a transparent background or you're saving a logo, icon, or screenshot. Use WebP if you manage a website and want smaller, faster loading images. Convert HEIC to JPG the moment you need to share an iPhone photo with anyone outside Apple's world. AVIF is a nice bonus if you're technical enough to manage it, but it's not essential for most people.
One more thing that matters more than most people realize: resizing a photo to the dimensions you actually need almost always saves more space than fiddling endlessly with the quality slider. A photo that's 4000 pixels wide doesn't need to stay that big if it's only ever displayed at 1200 pixels on a webpage.