When writing a blog, have you hesitated over “PNG or JPG for the image”? When building a website, have you considered WebP? Or stared blankly when your boss asks for an ICO icon? This post covers the underlying differences of PNG / JPG / WebP / ICO, when to use which, and how to batch convert. Pair with the Piick image converter and get it done in one click — no need to install ImageMagick.

The underlying differences of the three formats

The 4 mainstream bitmap formats have completely different compression approaches:

  • JPG (JPEG): Lossy compression, throws away details the human eye is less sensitive to (high-frequency info). Extremely high compression ratio (10-20% of original), every save loses quality. Best for photos — photos already have lots of noise, so losing a bit is invisible
  • PNG: Lossless compression, preserves every pixel. Supports alpha transparency, great for logos, icons, UI screenshots. Files are 3-5x larger than JPG, but can be saved repeatedly without loss
  • WebP: Format launched by Google in 2010, supports both lossy and lossless. Lossless is 26% smaller than PNG, lossy is 25-34% smaller than JPG, plus transparency and animation. Browser support is 96%+
  • ICO: Format for icons (.ico), typically containing multiple sizes like 16x16, 32x32, 48x48, 256x256. Used for Windows desktop shortcuts and favicons

Memory trick: JPG for photos, PNG for transparency, WebP for general use, ICO for icons.

When to use which format

A practical selection guide:

  • E-commerce product images, photography -> JPG (WebP also works)
  • Logos, icons, UI screenshots, semi-transparent images -> PNG
  • Web images (load speed matters) -> WebP (with JPG/PNG fallback)
  • Favicons, desktop shortcuts -> ICO
  • Print materials -> TIFF or PNG (lossless)
  • GitHub READMEs, technical blogs -> WebP or PNG

Pitfall guide:

  1. Don’t save logos as JPG — transparent backgrounds get filled with white, edges become lossy
  2. Don’t repeatedly save JPGs — every save loses detail; after 3 saves it’s noticeably blurry
  3. Don’t save photos as PNG — files become 5x larger, slower to load, no quality gain
  4. WebP isn’t universal — a few old browsers (IE) don’t support it, so you need fallback

Current state of WebP/AVIF browser support

WebP is now almost standard — Chrome / Firefox / Edge / Safari all support it, with roughly 97% global browser support in 2024. But 3% of users are on old browsers or special environments (older WeChat built-in browsers, corporate intranet IE), so keep fallback for important scenarios.

AVIF is a newer format, based on AV1 video encoding. It’s 20% smaller than WebP, but browser support is only around 95%, and encoding is slow. The 2026 choice: WebP is the default, AVIF is the advanced option, wait until 2027-2028 adoption grows before switching.

Practical one-click batch conversion

The Piick image converter supports JPG / PNG / WebP / ICO 4-way conversion, with up to 50 images processed in one batch:

  1. Drag a batch of images into the upload area (supports JPG/PNG/WebP/GIF input)
  2. Pick the target format — for example, select WebP for all
  3. Click “Convert” — processed one by one with live progress
  4. When all done, automatically packaged into ZIP for download (uses jszip for client-side packaging, no upload)

Notes:

  • GIF animations can only convert the first frame — batch ICO conversion also only keeps the first frame
  • Conversion automatically strips EXIF metadata (including GPS location) — this is a privacy feature, not a bug
  • Runs locally in the browser, no upload, no compression loss (uses Canvas toBlob)

JPG to PNG can’t preserve quality — Canvas decoding has already lost some. But PNG to WebP in lossless mode can preserve 100%.

Open the Piick image converter now, drag in a few photos, batch convert to WebP, and watch the file size change.