Image Formats Explained: A Field Guide
A plain-language map of the formats you actually run into — what each is good at, what it's terrible at, and which one to reach for.
There are only a handful of image formats you'll ever actually meet, and each one exists because it's good at a job the others do badly. Learn what each is for and most format decisions answer themselves. This is the short field guide — what to reach for, what to avoid, and the babapic tool that converts it when you're handed the wrong one.
The formats at a glance
For photographs: JPG, HEIC, WebP
JPG is the default photograph format: lossy, small, and readable by everything since the 1990s. It's what most forms and print services expect. Its one weakness is repeated re-saving — see generation loss.
HEIC is what your iPhone shoots by default. It's more efficient than JPG but barely supported off Apple devices, so it's the classic "won't open" file — HEIC to JPG fixes that, and our HEIC guide explains why the phone does it.
WebP is the modern option: smaller than JPG at the same quality, but not universally accepted yet. Great for the web, awkward off it. Full story in the WebP explainer.
For graphics and transparency: PNG, WebP, SVG
PNG is lossless and keeps a transparent background — the right home for logos, icons, screenshots of text, and line art. It's a poor choice for photographs, where it balloons. The whole comparison is in JPG vs PNG.
WebP keeps transparency too, at a smaller size than PNG — the trade is compatibility, laid out in PNG vs WebP.
SVG is different in kind: it stores drawing instructions, not pixels, so it stays razor-sharp at any size. Perfect for logos and icons, useless for photos. When something won't accept it, SVG to PNG rasterizes it — but keep the SVG, because you can't get it back.
For animation: GIF
GIF is capped at 256 colours and has no real motion compression, so it's heavy for what it shows. It survives out of habit and reach. If you only need one frame, GIF to PNG grabs a still; if you need it lighter, our guide to shrinking a GIF is honest that a video is usually the real answer.
For documents: PDF
PDF isn't an image format so much as a fixed-layout wrapper — which is exactly why forms ask for it. Image to PDF turns a photo or scan into one, and Merge Images to PDF combines several into a single ordered file. See turning a photo into a PDF for what the conversion does to your image.
The awkward one: BMP
BMP is essentially raw, uncompressed pixels — so a BMP can be many times the size of the same picture as a JPG, for no visible benefit. If you've been handed one, BMP to JPG shrinks it dramatically, and our guide on opening a BMP anywhere covers why it exists at all.
How to choose, in one line each
- Photograph? JPG, or WebP for the web.
- Logo, icon, screenshot of text? PNG, or SVG if you have the vector.
- Needs a transparent background? PNG or WebP — never JPG.
- Going into a form that wants one file? PDF.
- Handed a HEIC, WebP or BMP your software won't open? Convert it to JPG or PNG.
FAQ
What's the most compatible image format?
JPG for photographs and PNG for graphics — both open in essentially everything. Reach for them when a file has to work on someone else's machine.
What's the best format for the web?
WebP, for the smaller files and faster pages — with JPG or PNG as a fallback for the occasional tool or browser that still won't take WebP.
Which format should I use for a photo with a transparent background?
There's no such thing as a transparent photograph in JPG, and a full photo rarely needs transparency — but if you've cut a subject out, save the result as PNG or WebP. JPG would flatten the transparency to white.