Understanding image formats
PNG, JPG, WebP, AVIF, HEIC.
A short tour of the formats every modern phone, browser and camera disagrees about — and how to pick the right one.
Lossless vs lossy.
PNG is lossless: every pixel survives a round-trip exactly. JPG is lossy: it throws away high-frequency detail in a way the eye barely notices, in exchange for a much smaller file. That's the central trade-off — keep the bytes (PNG) or keep the bandwidth (JPG). Photographs, where every pixel is slightly noisy anyway, lose almost nothing visually with JPG at quality 85. Screenshots, diagrams, line art — anything with sharp edges and flat colour — fare badly under JPG and should stay PNG.
lossless: PNG, WebP-lossless lossy: JPG, WebP, AVIF, HEIC
WebP — the modern in-between.
WebP, designed by Google in 2010, supports both lossless and lossy modes plus alpha transparency and animation in a single container. At equivalent quality, lossy WebP is typically 25–35% smaller than JPG; lossless WebP is 25% smaller than PNG. It became universally supported around 2020 and is now the safe default for the web. Older tools, photo viewers and messaging apps may still refuse it, which is why the web-to-everything-else bridge usually means converting WebP back to JPG or PNG.
AVIF — the next generation.
AVIF (AV1 Image File Format) arrived around 2019 and uses the AV1 video codec's intra-frame coding for stills. At equal visual quality it's roughly 50% smaller than JPG and 20% smaller than WebP. Browser support is now broad (Chrome, Edge, Firefox, Safari 16+) but native OS support lags — Windows and macOS only added system-wide AVIF readers in the last few releases. For static web assets it's worth adopting; for files you'll send around, JPG or WebP is still friendlier.
HEIC — Apple's choice.
HEIC is the iPhone's default since iOS 11. It uses the HEVC video codec and produces files about half the size of JPG at comparable quality. Decoding it requires HEVC, which is patent-encumbered and not on every machine — Windows users historically needed an extension from the Microsoft Store, and many web tools still don't read it natively. Hence the steady demand for HEIC-to-anything conversion. iPhones can be told to capture in JPG instead under Settings → Camera → Formats → Most Compatible.
JFIF is JPG, mostly.
A file ending in .jfif contains JPEG-encoded bytes wrapped in the JFIF container — the same picture, just a slightly different header. Windows occasionally saves attachments as .jfif instead of .jpg, which confuses some apps and websites that key off the file extension. Renaming the file fixes it about half the time; re-saving as a clean .jpg always does.
Picking, in practice.
For the web, lean on WebP for new work and let your image pipeline emit AVIF as a richer fallback. For sharing with humans, send JPG — the universal language of consumer photography. For screenshots and UI assets, keep PNG. For icons and line art, use SVG. The right answer is almost always the format the receiving system expects with the smallest size that doesn't hurt the picture.
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