You take a photo on your phone, try to upload it to a website, and get an error: "unsupported format." Or you save a screenshot and the text looks fuzzy. Or a simple logo somehow takes up five megabytes. Image formats cause a surprising amount of everyday frustration, but the basics fit on one page. Here is a plain-English guide to the formats you are most likely to meet.
JPG: the all-rounder for photos
JPG, also written JPEG, is the most widely supported image format in the world. It uses lossy compression, meaning it throws away detail the eye is unlikely to notice in order to make files smaller. That works brilliantly for photographs, with their smooth gradients and natural textures. It works badly for screenshots, text and logos, where compression creates blurry edges and blocky artifacts.
Use it for: photos you want to share, email or upload almost anywhere.
PNG: sharp edges and transparency
PNG uses lossless compression, so nothing is thrown away. Text stays crisp, and flat colors stay flat. PNG also supports transparency, which is why logos and icons often come as PNG files. The downside is size: a photograph saved as PNG can be several times larger than the same photo as JPG.
Use it for: screenshots, diagrams, logos and anything with text.
WebP: the modern web format
WebP was designed for websites. It can be lossy or lossless, supports transparency, and is usually noticeably smaller than JPG or PNG at similar quality. All modern browsers support it. Some older desktop software and some upload forms still do not, which is the main reason to convert out of it.
Use it for: images on your own website, where smaller files mean faster pages.
HEIC: the iPhone default
Recent iPhones save photos as HEIC by default. It offers good quality at small sizes, but many websites, Windows programs and online forms cannot open it. This is the most common source of "unsupported format" errors. Converting HEIC to JPG before uploading solves the problem, or you can change the camera setting to "Most Compatible."
A note on GIF and SVG
GIF is old and limited to 256 colors, but it lives on for short animations. SVG is not a pixel image at all but a set of drawing instructions, perfect for logos and icons that need to scale to any size without blurring.
How to convert and compress safely
When you need to switch formats or shrink a file, look for a tool that runs in your browser without uploading your photos to a server. FileOtter's image compressor works locally and lets you compare quality before saving, which is useful for personal photos and work images alike.
- Resize before compressing. A 4000-pixel photo shown at 800 pixels wastes most of its data.
- Keep an original copy. Every lossy save loses a little more detail.
- Check the result at full size, especially around text and edges.
The cheat sheet
- Photo to share: JPG.
- Screenshot or logo: PNG.
- Image for your website: WebP.
- iPhone photo that will not upload: convert HEIC to JPG.
- Icon that must scale: SVG.
Once you know which format suits which job, most image headaches simply disappear, and your files become smaller, sharper and easier to share.
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