Image and document format reference

Lossy, no transparency, universally supported by every browser, printer, portal and phone made in the last thirty years. Compression is cumulative: each re-save of an already compressed JPG discards more detail, visible first on text edges and flat gradients. Choose JPG when the receiving system is old, unknown, or explicitly asks for JPG. Quality 75-85 is usually indistinguishable from the original at normal viewing size; below 50 blocking artefacts appear around high-contrast edges.

Lossless with full alpha transparency. Ideal for logos, screenshots of text, diagrams and anything with flat colour or hard edges, because lossless means no artefacts around type. Poor for photographs: a photo saved as PNG is typically 4-10x larger than the same photo as a quality-85 JPG, since PNG's compression exploits repeated colour, which photographs do not have. If a PNG screenshot is too heavy, convert to WebP rather than JPG so you keep the sharp text.

Supports both lossy and lossless modes plus transparency, and is supported by every current browser. At visually comparable quality WebP is commonly 25-35% smaller than JPG for photographs and often smaller than PNG for graphics with transparency. The trade-off is outside the browser: some older desktop software, print workflows and government upload portals still reject .webp. Use it for websites and app assets; convert back to JPG or PNG when submitting to a portal.

Based on the AV1 video codec. Typically the smallest of the four at a given perceived quality, frequently well below WebP, with transparency and wide colour support. Costs are encode time (noticeably slower in a browser, especially on phones) and compatibility: support is good in current browsers but poor in older software and many upload systems. Best for a website you control and can serve with a JPG fallback.

Apple's default camera format. Efficient, but not accepted by most Windows software, Nigerian and international upload portals, or older browsers, which is why a photo that looks fine on an iPhone is often rejected on submission. Convert HEIC to JPG before uploading anywhere that has not explicitly said it accepts HEIC.

A PDF can hold vector text, embedded fonts and images all at once, which is why PDF size depends far more on what is inside than on the page count. A ten-page text PDF exported from a word processor is often under 200 KB; a two-page scan of the same document can exceed 10 MB because each page is a full-resolution photograph. That distinction matters when a file is too big for email: compressing a scanned PDF works well, while compressing a text PDF that is already small changes almost nothing.

Photograph going to a portal or printer: JPG. Screenshot, logo or anything with text: PNG, or WebP if size matters. Website you control: WebP, or AVIF with a JPG fallback. iPhone photo going anywhere else: convert to JPG. Multi-page document: PDF, and compress it only if the pages are scans.