JPEG vs PNG vs WebP vs AVIF vs HEIC
What each format is actually good at, not a spec sheet.
Every format question here reduces to the same two: what's in the picture, and where is it going. A photo behaves nothing like a screenshot once you start compressing it, and "needs a transparent background" rules out an entire category on its own. Below are the three formats this tool outputs — JPEG, WebP, PNG — and the two it reads and converts away from, AVIF and HEIC, along with the reason a conversion step exists for those two at all.
JPEG
JPEG discards the detail a human eye is least likely to miss, which is exactly why a photograph compresses down so much smaller in JPEG than it would losslessly. Point that same trick at a screenshot or a line of text and it falls apart — the compression blurs sharp edges and introduces visible blocking that a photo mostly hides. No transparency channel, full stop. What JPEG has going for it thirty years on is that literally everything opens it.
PNG
Nothing gets thrown away. Screenshots, logos, and line art come out pixel-identical to the source, with a real alpha channel for transparency. The price is size — a PNG of a photograph routinely runs several times heavier than a JPEG most people can't tell apart visually. There's no quality dial to turn down here, so this tool's PNG search works the palette instead — how many distinct colors the image gets to keep — which is also why compressing a busy photographic PNG takes noticeably longer than a flat graphic with a handful of colors to begin with.
WebP
One format, both compression styles: WebP does lossy and lossless, generally beats JPEG's size at equal visual quality for photos, and carries transparency the way PNG does — which covers most of what would otherwise need both formats. Every browser in current use supports it. The remaining case for JPEG or PNG specifically is compatibility — an older CMS, a print house's upload spec, something that hasn't been touched in a decade.
AVIF
Smaller than WebP again at matching quality, plus HDR on top of transparency — on the numbers, the winner. What it costs is time: a single AVIF encode runs well past a second even on capable server hardware, against under 100ms for JPEG or WebP. Nothing for a one-off export. A real problem for a server binary-searching quality across dozens of candidate encodes per upload, which is exactly why this tool doesn't offer it as an output format — a known gap, not an oversight.
HEIC / HEIF
Apple's default photo format since 2017, and it compresses noticeably smaller than JPEG at comparable quality — the tradeoff is that plenty of software, older browsers, and non-Apple devices still can't open it. This tool detects HEIC/HEIF on the way in and decodes it automatically before compressing, so an iPhone photo can go straight in and come back as JPEG, WebP, or PNG with no separate conversion step first.
Once it's lossy, it's lossy for good
Save a JPEG, WebP, or AVIF at lossy quality, and whatever it discarded is gone permanently — re-saving that result as PNG afterward doesn't recover it, it just locks the already-degraded image into a bigger file. Keep an original around if there's any chance you'll need to re-edit later, and always compress from that original again rather than from a previous export.
By use case
Photo headed to the web or social: WebP, JPEG if compatibility matters more than size. Screenshot, logo, anything with text or hard edges: PNG. Needs a transparent background: WebP or PNG. An iPhone photo you need to send somewhere that won't take HEIC: this tool converts it automatically. Not sure and just need it smaller: WebP is the closest thing to a safe universal default right now.
From there, compress to an exact target size rather than a quality guess — or check current upload size limits by platform if there's a specific cap involved.