Every time you export an image, you're making a trade-off between file size, visual quality, and compatibility. The format you choose determines how that trade-off plays out — and the wrong choice either bloats your file unnecessarily or introduces visible compression artifacts.
This guide explains when to use JPG, PNG, and WebP so you can make the right call without spending time second-guessing it.
The short version
If you want the answer before the explanation:
- Photograph or real-world image? → JPG (or WebP for web)
- Logo, screenshot, graphic, or text? → PNG
- Delivering any image on the web? → WebP (smaller than JPG and PNG at equal quality)
How JPEG compression works
JPEG is a lossy format. When you save a JPEG, the compression algorithm groups similar-colored pixels together and replaces the precise values with approximations. The result is a much smaller file — at the cost of some data.
For photographs, this trade-off is almost invisible. Human eyes are poor at distinguishing fine color variations in areas of gradual transition, and JPEG compression specifically targets those areas. At 80–85% quality, a JPEG photograph looks virtually identical to the uncompressed original at 20–30% of the file size.
Where JPEG fails is on hard edges and high contrast areas — text, line art, logos, and screenshots with sharp boundaries. In those areas, adjacent pixels have very different values, and JPEG's approximation produces visible blocky artifacts called "ringing" around edges.
Use JPEG for: Photos, portraits, landscapes, product photography, any real-world image. Avoid JPEG for: Logos, text overlays, screenshots, graphics with flat color areas or sharp edges.
How PNG compression works
PNG is lossless. Every pixel is stored exactly as it is — no approximation, no data loss. The compression algorithm finds patterns in the image data and encodes them efficiently, but it never discards any information.
The result is a larger file than JPEG for photographs (sometimes 5–10× larger), but perfect fidelity for anything with hard edges, text, or transparency. PNG also supports an alpha channel — a transparency layer — which JPEG does not.
Use PNG for: Logos, screenshots, UI graphics, any image with text overlaid, images that need a transparent background. Avoid PNG for: Photographs where file size matters (the lossless storage produces unnecessarily large files).
How WebP compression works
WebP is Google's modern image format that supports both lossy and lossless compression. In lossy mode, WebP consistently produces files 25–35% smaller than equivalent-quality JPEG. In lossless mode, WebP produces files 20–30% smaller than PNG.
WebP also supports transparency (like PNG) and animation (like GIF).
Browser support is now excellent — all modern browsers support WebP. The main limitation is older tools and platforms that don't accept WebP uploads.
Use WebP for: Any image delivered via a web browser — blog thumbnails, landing page images, OG images. Also a great export choice for social posts that allow it. Avoid WebP for: Platforms that don't accept it (most social media upload forms still require JPG or PNG).
Format comparison at a glance
Quality settings explained
JPEG and lossy WebP have a quality slider (typically 0–100%). The right setting depends on your use case:
- Social media post images: 80–85% — visually lossless, meaningfully smaller file
- Thumbnails / previews: 70–75% — acceptable quality at very small file size
- Archival or printing: 90–95% — preserve maximum detail
- Never use 100% for delivery — the file size increase is huge for negligible quality gain
PNG and lossless WebP have no quality setting — only compression level, which affects file size and encoding speed but not pixel accuracy.
The "save for web" trap
Many image editors have a "Save for Web" mode with preset quality settings. These presets often default to conservative quality levels (60–70%) that produce visibly degraded results. Always check the actual quality value when exporting rather than relying on named presets like "Good" or "Optimized."
ImageSizeTool lets you choose your export format and see the estimated file size before you download, so you can dial in the right quality without guessing.