Every image on your phone or computer is stored in some format — JPG, PNG, WebP, HEIC, GIF — and most format frustration comes from one simple fact: each format was designed for a different job. A format brilliant for photos is terrible for logos; the format your iPhone loves is one an upload form may reject.
The good news: there are only about six formats you will ever meet, each has a one-line job description, and converting between them takes seconds in a browser. This guide gives you the map — what each format is for, what conversion actually does to your image, and a decision table you can keep.
The one idea behind every format: lossy vs lossless
Before the formats themselves, one distinction explains almost everything: how a format compresses the image data.
- Lossless compression shrinks a file while keeping every pixel exactly as it was — like zipping a folder. Open it and you get a perfect original back. PNG works this way.
- Lossy compression shrinks a file by discarding detail your eye is unlikely to notice — subtle color gradations, fine texture. The file gets far smaller, but the discarded detail is gone for good. JPG works this way.
Neither is "better." Lossy is spectacular for photographs, where millions of subtly varying pixels hide the losses. Lossless is essential for screenshots, logos, and text in images, where every crisp edge matters and lossy compression smears artifacts around sharp lines.
One rule falls straight out of this: converting can never restore quality. Turning a JPG into a PNG doesn't bring back what JPG discarded — it just wraps the already-lossy image in a lossless container, usually making the file bigger for no visual gain. Convert to serve compatibility or size, never in the hope of "upgrading" an image.
The formats, one by one
JPG (JPEG) — the photograph workhorse
JPG (or JPEG, for the Joint Photographic Experts Group that created it) is the world's default photo format. It uses lossy compression tuned for exactly what photos contain: smooth gradients, natural texture, millions of colors. At sensible quality settings, a JPG looks essentially identical to the original at a fraction of the size.
Use it for: photographs going anywhere — email, documents, most websites. Weaknesses: no transparency; sharp-edged graphics (text, logos, screenshots) develop visible "ringing" artifacts; re-saving a JPG repeatedly compounds quality loss, because each save discards a little more.
PNG — screenshots, logos, and transparency
PNG (Portable Network Graphics) is the lossless everyday format. Every pixel is preserved, and it supports transparency — the see-through background that lets a logo sit cleanly on any color.
Use it for: screenshots, logos, icons, charts, any image containing text, and anything needing a transparent background. Weakness: photographs. A photo saved as PNG is often several times larger than a visually identical JPG, because lossless compression can't exploit what eyes don't notice.
WebP — the modern web all-rounder
WebP is a newer format built for the web, and it can do both lossy and lossless compression — plus transparency and animation. Its compression is more efficient than JPG's and PNG's, meaning smaller files at comparable quality, which is why websites increasingly serve WebP and why files you save from the web often turn out to be .webp.
Use it for: images on websites — smaller files mean faster pages. Weakness: compatibility outside browsers. All modern browsers display WebP, but some older desktop software, upload forms, and workplace systems still don't accept it. That mismatch — "the web gave me WebP, my tool wants JPG or PNG" — is one of the most common conversion needs today.
AVIF — newer still, smaller still
AVIF is the next generation after WebP, derived from the AV1 video codec. It typically compresses even more efficiently — noticeably smaller files at similar quality — and supports transparency and high dynamic range. Modern browsers now display it, but general software support is still catching up, so treat it like WebP's younger sibling: excellent where it's accepted, and easy to convert to JPG/PNG where it isn't.
HEIC — the iPhone format
HEIC (High Efficiency Image Container) is what iPhones save photos in by default. Apple adopted it because its modern compression stores photos in noticeably smaller files than equivalent-quality JPGs — a real benefit for a phone full of pictures.
The catch is compatibility: Windows PCs, older software, many websites, and plenty of upload forms don't handle HEIC without extra steps. This is the classic "my photos won't open on my PC" problem, and the standard fix is simply converting HEIC to JPG — the photo itself is untouched apart from the format change (a lossy-to-lossy conversion, so use a good quality setting and keep the originals). You can also tell an iPhone to shoot in JPG directly (Settings → Camera → Formats → Most Compatible) if you trade some storage for zero friction.
GIF — animation's grandparent
GIF is ancient by computing standards and survives for one reason: simple looping animation that plays literally everywhere. As a still-image format it is obsolete — it can only store 256 colors, so photos look posterized. Even for animation it is inefficient; short video clips or animated WebP are far smaller. But when compatibility of a small looping animation is everything, GIF still delivers.
The decision table
| You have… | Use | Why |
|---|---|---|
| A photograph to share or embed | JPG | Small, universal, looks great for photos |
| A screenshot or image with text | PNG | Lossless keeps edges and text crisp |
| A logo needing a transparent background | PNG | Transparency + lossless edges |
| Images for your own website | WebP (or AVIF) | Smallest files, faster pages |
| iPhone photos your PC/form rejects | Convert HEIC → JPG | Universal compatibility |
| A short looping animation | GIF (or animated WebP) | Plays everywhere |
A .webp your software refuses |
Convert WebP → JPG/PNG | Match the tool's expectations |
Resizing and compressing: the other half of image handling
Format choice is half the story; size is the other half. Two different levers shrink an image file, and they are often confused:
- Resizing changes the pixel dimensions — a 4000×3000 phone photo becomes, say, 1600×1200. Fewer pixels, dramatically smaller file. For screens this is usually free savings: a photo viewed in a chat window or web page simply doesn't need 12 million pixels.
- Compressing keeps the dimensions but re-encodes with stronger (lossy) compression — a lower JPG quality setting, for instance. Smaller file, some detail traded away.
For big reductions, resize first, then compress moderately — that combination usually beats aggressive compression alone, and it's the same logic behind shrinking image-heavy PDFs, which our PDF tools guide covers. For the full size-reduction toolbox across every file type, see the guide to making files smaller.
A related, privacy-flavored note: photos carry metadata (EXIF) — camera model, settings, sometimes the GPS location where the shot was taken. Many platforms strip it on upload, but not all. If you're posting a photo publicly, stripping metadata during conversion is a sensible habit.
Converting images without regret
Three habits make image conversion painless:
- Keep the original. Convert a copy, especially when the target is lossy. Storage is cheap; a discarded original isn't recoverable.
- Convert for a reason — compatibility (HEIC→JPG, WebP→PNG), transparency (→PNG), or size (→WebP/JPG). Never expect conversion to improve quality.
- Use a tool that states its behavior. A good converter tells you its quality settings, its file-size limits, and — since you're uploading personal photos — exactly when uploads are deleted.
Everyday image conversion is precisely what Multiflay is being built for: a free, browser-based toolkit that converts between PNG, JPG, WebP, AVIF, HEIC, and GIF, with compression, resizing, and metadata stripping — and uploads that auto-delete on a stated schedule.
FAQ
What's the difference between PNG and JPG in one sentence?
JPG uses lossy compression that makes photographs small and great-looking; PNG uses lossless compression that keeps screenshots, logos, and text pixel-perfect and supports transparency — pick by content, not habit.
Why do my iPhone photos come out as HEIC, and how do I open them on Windows?
Apple uses HEIC because it stores photos in significantly smaller files than JPG at similar quality. Windows and many upload forms have patchy support, so the practical fix is converting HEIC files to JPG, or setting the iPhone camera to "Most Compatible" so it shoots JPG in the first place.
Does converting a JPG to PNG improve its quality?
No. Whatever detail JPG compression discarded is permanently gone; converting to PNG just stores the already-degraded image losslessly, typically in a much larger file. Convert JPG to PNG only when you need a format a tool insists on — never for quality.
Which image format is best for a website?
WebP is the strong default: smaller files than JPG or PNG at comparable quality, with transparency and animation support, and every modern browser displays it. AVIF is even more efficient where supported. Keep JPG/PNG fallbacks only if you must support very old software.
Got a stubborn image file? Multiflay is a free, browser-based file toolkit — convert between PNG, JPG, WebP, AVIF, HEIC, and GIF, compress, resize, and strip metadata, with uploads that auto-delete. Drop a file, get the format you need, at multiflay.com.
