Image Formats Explained
A reference table for every format the Bytewitness converter supports — what each one actually is, when it's the right choice, and what it can and can't do.
Format comparison table
| Format | Compression | Best for | Transparency | Typical size (photo) | Browser support |
|---|---|---|---|---|---|
| JPG / JPEG | Lossy | Photographs, web images where size matters | None | Small (200KB–1MB for typical photos) | Universal |
| PNG | Lossless | Graphics, screenshots, logos, UI, transparency | Full alpha channel | Large (2–10× JPG for photos) | Universal |
| WebP | Lossy or lossless (selectable) | Web use — photos and graphics, modern browsers | Full alpha channel | 25–35% smaller than JPG / 25% smaller than PNG | All modern browsers (Chrome, Firefox, Safari 14+, Edge) |
| GIF | Lossless, 256 colors max | Simple animations, simple graphics (legacy) | Single-color (one transparent index) | Varies; poor for photos due to 256-color limit | Universal |
| BMP | None (uncompressed) | Legacy Windows applications; source files | Rarely (non-standard) | Very large (uncompressed raw pixels) | Universal (rarely served on web) |
| HEIC / HEIF | Lossy (HEVC / H.265) | iPhone photos; Apple devices (iOS 11+) | Yes (full alpha) | ~½ size of equivalent JPEG | Native on macOS/iOS; requires plugin on Windows; limited on Android |
Format details
JPG / JPEG
Created in 1992, JPG uses the Discrete Cosine Transform (DCT) algorithm to achieve dramatic file size reductions by discarding high-frequency detail the human eye is less sensitive to. At quality settings of 85–95, most people can't distinguish a JPG from the lossless original at normal viewing sizes. Every re-save accumulates more loss — if you edit and re-save repeatedly, use PNG or WebP lossless as your working format and export JPG only for the final deliverable.
PNG
PNG (Portable Network Graphics) was designed in 1996 as a patent-free replacement for GIF, with full color support. It uses DEFLATE compression — lossless, meaning every pixel is stored exactly. This makes PNG ideal for anything where pixel accuracy matters: UI screenshots, logos, graphics with text, and images you'll edit repeatedly. The tradeoff is file size: photographs stored as PNG are typically 3–10× larger than equivalent JPGs.
WebP
Google developed WebP in 2010 using VP8 compression for lossy mode and a variant of DEFLATE for lossless. It consistently outperforms JPG and PNG at equivalent quality — about 25–35% smaller than JPG for photos, 25% smaller than PNG for graphics. WebP also supports full transparency and animation. Browser support is now effectively universal for modern web use.
GIF
GIF (1987) is a 256-color format best known for animation. Its 256-color palette makes it unsuitable for photographs — gradients and photographic detail produce visible banding. For static images, PNG is almost always a better choice: better compression, full color depth, no palette limitation. GIF's niche today is simple, short animations where WebP or APNG aren't supported.
BMP
BMP (Bitmap) stores raw pixel data with no compression. Files are exactly width × height × bytes-per-pixel in size, which makes them very large with no quality advantage over lossless formats. BMP is mainly encountered in Windows applications, legacy software, and as source material. Convert to PNG for lossless preservation or JPG for photographs.
Frequently asked questions
Convert between any of these formats free → Use the Bytewitness converter — browser-based, no upload, no account required.