How to Compress Images Without Losing Quality — Real Test Results
What truly lossless vs visually lossless actually means, where JPEG quality loss becomes visible, and practical compression settings measured with Utilao's own compressor.
HEIC, AVIF, WebP, PNG, or JPG: Which Image Format Should You Use?
Five formats, five different trade-offs. What each one is actually good at, whether it supports transparency, and when converting between them makes sense.
Same Picture, Five Different Containers
The pixels in a photo don't change based on file format — what changes is how those pixels get compressed and stored, and what extra capabilities (like transparency) the format supports. Picking the right one is really about matching the format's trade-offs to what you're going to do with the image.
The Five Formats, Practically
JPG (JPEG) — the oldest and most universally supported format here. Lossy compression, no transparency, excellent for photographs. If you need a file to open correctly absolutely everywhere — old software, every device, every platform — JPG is still the safest default.
PNG — lossless compression, full transparency support (alpha channel). The right choice for screenshots, logos, diagrams, and anything where every pixel must stay exact, or where transparency is required and you're not sure the destination supports newer formats. The cost: PNG files are much larger than JPG for photographic content, since lossless compression can't discard the fine detail a photo doesn't need.
WebP — Google's web-focused format. Supports both lossy and lossless modes, and supports transparency. Typically produces meaningfully smaller files than JPG at similar visual quality, and smaller than PNG when transparency is needed. Browser support is now essentially universal; the remaining gap is non-web software that hasn't added support.
AVIF — newer than WebP, generally achieving even smaller files at a given quality, and also supports transparency. The trade-off is compatibility: AVIF support is solid in current browsers but noticeably less universal in older software, some image editors, and some platforms than JPG, PNG, or even WebP. Worth using where you control the viewing environment (your own website, an app you control); worth double-checking before using where you don't.
HEIC (HEIF) — the default photo format on recent iPhones. Efficient compression similar in spirit to AVIF, but primarily an input format you'll encounter (a photo someone sent you, or your own camera roll) rather than one you'd deliberately choose to create. Support for opening HEIC files outside Apple's ecosystem is inconsistent — many Windows programs, older browsers, and various online tools can't open it directly, which is the single most common reason people convert HEIC to JPG or PNG.
Transparency Support at a Glance
| Format | Transparency | Compression |
|---|---|---|
| JPG | No | Lossy only |
| PNG | Yes | Lossless |
| WebP | Yes | Lossy or lossless |
| AVIF | Yes | Lossy or lossless |
| HEIC | Yes (rarely used in practice) | Lossy or lossless |
Converting a transparent image (PNG, WebP, AVIF) to JPG removes the transparency — the transparent areas get filled with a background color, since JPG has no way to represent "no color here." Always convert to a transparency-capable format if you need to preserve it.
When Conversion Actually Makes Sense
HEIC → JPG or PNG: almost always about compatibility — you have a photo from an iPhone and need it to open in software, a website, or a device that doesn't handle HEIC. This is the most common reason people reach for a converter.
PNG → JPG: when the image is a photograph (not a graphic needing pixel-perfect exactness or transparency) and file size matters more than lossless quality. A photographic PNG can easily be 5–10x larger than an equivalent-quality JPG.
JPG/PNG → WebP or AVIF: when you control where the image will be viewed (your own website) and want smaller files without a visible quality difference — the most common reason for site performance work.
AVIF or WebP → JPG/PNG: when you're sending an image somewhere you're not sure supports the newer format — older software, a print shop, a platform with unclear format support.
What This Guide Isn't
This isn't a guide to every possible format-pair conversion — it's a decision guide for picking the right format for a purpose. For step-by-step conversion instructions, use the Convert Image tool directly: upload your file, pick the output format from the list of currently supported formats, and download the result. It handles quality settings for lossy formats and lets you choose what happens to transparency when converting to a format that doesn't support it.
FAQ
Is AVIF always better than WebP? Usually smaller at the same visual quality, but with narrower compatibility. For anything you don't fully control the viewing environment for, WebP is currently the safer bet; for AVIF, check where the image needs to work first.
Why can't I open a HEIC file I received? Support for HEIC varies a lot outside Apple devices. Convert it to JPG or PNG with the Convert Image tool for universal compatibility.
Does converting JPG to PNG recover lost quality? No. Once JPG's lossy compression has discarded detail, converting to a lossless format afterward just stores the already-reduced quality in a bigger file — it doesn't undo anything.
Which format should I use if I'm not sure? JPG for photos without transparency, PNG for anything needing transparency or pixel-perfect exactness, and WebP if you specifically control a website and want smaller files with wide, current browser support.
Ready to convert? Use the Convert Image tool — pick your output format, adjust quality if needed, and download.