FIRST CH TOOLS LOCAL PROCESSING — IMAGES NEVER LEAVE YOUR DEVICE 日本語

FIRST CH TOOLS / 12 AVIF CONVERTER

Batch Image → AVIF Converter + <picture> Snippet

Converts PNG/JPEG images to AVIF and generates a ready-to-paste <picture> snippet. Supports batch conversion and ZIP download. All processing happens on your device.

Drag & drop images here or click to choose files (PNG / JPEG, multiple allowed)
45–60 is a practical range (AVIF stays sharp at lower values than WebP/JPEG; higher = better quality, larger files)

How to Use

  1. Set the qualityPick 1–100 with the slider. AVIF looks great even at 45–60.
  2. Choose imagesDrag & drop or click to select PNG/JPEG files (multiple allowed). Conversion starts immediately.
  3. Save & copySave the AVIF files (one by one or as a ZIP), then copy the <picture> snippet into your HTML and fill in alt.

About This Tool

AVIF is a modern image format based on the AV1 video codec. At the same quality it is often even smaller than JPEG/WebP, which helps page speed and Core Web Vitals. Because a few older environments still lack support, the practical approach is a <picture> element that prefers AVIF while keeping the original JPEG/PNG as a fallback. The snippet this tool generates follows that pattern and includes width/height and loading="lazy" to avoid layout shift. Conversion runs libavif compiled to WebAssembly inside your browser, so your images are never uploaded to any server — safe even for logos and unreleased designs.

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