Image Info - Complete Guide

Image info extracts metadata and properties from image files: dimensions (width/height), file size, format (JPEG, PNG, GIF, WebP), color depth, EXIF data (camera, GPS, date), and compression details. Essential for photo management, web optimization, and digital forensics.

How It Works

Read image file headers and metadata blocks. JPEG stores EXIF in APP1 marker, PNG uses tEXt/iTXt chunks, GIF has logical screen descriptor. Parse binary structure to extract properties without decoding full image data.

Technical Details

Image formats: JPEG (lossy, EXIF), PNG (lossless, alpha), GIF (256 colors, animation), WebP (modern, both lossy/lossless). EXIF includes: camera make/model, exposure, ISO, GPS coordinates, datetime. File signature (magic bytes) identifies format.

Common Use Cases

1. Photo Management: Sort photos by date, location, camera.
   • Example: Organize by EXIF date taken
2. Web Optimization: Check dimensions and size before upload.
   • Example: Resize 4000x3000 to 1200x900
3. Digital Forensics: Examine metadata for authenticity.
   • Example: Check if photo was edited
4. Accessibility: Verify images have appropriate dimensions.

Code Examples

Read Image Info

// Basic image dimensions (browser)
function getImageInfo(file) {
  return new Promise((resolve) => {
    const img = new Image();
    const url = URL.createObjectURL(file);

    img.onload = () => {
      resolve({
        name: file.name,
        type: file.type,
        size: file.size,
        width: img.naturalWidth,
        height: img.naturalHeight,
        aspectRatio: (img.naturalWidth / img.naturalHeight).toFixed(2)
      });
      URL.revokeObjectURL(url);
    };

    img.src = url;
  });
}

// Format file size
function formatSize(bytes) {
  if (bytes < 1024) return bytes + ' B';
  if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
  return (bytes / (1024 * 1024)).toFixed(2) + ' MB';
}

// Detect format from magic bytes
async function detectFormat(file) {
  const buffer = await file.slice(0, 12).arrayBuffer();
  const bytes = new Uint8Array(buffer);

  // Check signatures
  if (bytes[0] === 0xFF && bytes[1] === 0xD8) return 'JPEG';
  if (bytes[0] === 0x89 && bytes[1] === 0x50) return 'PNG';
  if (bytes[0] === 0x47 && bytes[1] === 0x49) return 'GIF';
  if (bytes[8] === 0x57 && bytes[9] === 0x45) return 'WebP';
  return 'Unknown';
}

Browser-based image info extraction. For EXIF, use libraries like exif-js or piexifjs.

Tips & Best Practices

• Check both file size and dimensions for web use
• Strip EXIF for privacy before sharing
• Verify format matches extension
• Consider color profile for print work
• Use libraries for full EXIF extraction

Common Mistakes to Avoid

• Ignoring GPS data privacy implications
• Confusing file size with decoded size
• Trusting file extension over magic bytes
• Not handling missing metadata gracefully

When to Use This Tool

Use image info when managing photo libraries, optimizing images for web, verifying image properties, or extracting metadata for analysis.

Frequently Asked Questions

What EXIF data can be extracted?

Camera make/model, lens, exposure settings (aperture, shutter, ISO), date/time, GPS coordinates, software used, orientation, flash, color space. Not all images have EXIF (PNG/GIF rarely do).

Can EXIF data be removed?

Yes, for privacy. Many tools strip EXIF on export. Social media often removes EXIF on upload. GPS data is privacy-sensitive. Use EXIF stripping tools before sharing.

How accurate is file size reporting?

Exact for file on disk. Decoded/uncompressed size differs: a 1MB JPEG might be 20MB when decoded to pixels. Consider both for different purposes.

What about color profile?

ICC profile embedded in image defines color space (sRGB, Adobe RGB, Display P3). Important for accurate color reproduction. Not all tools read/preserve profiles.

Get Started

Ready to try Image Info? Use the tool now - it's free, fast, and works right in your browser.

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Last updated: June 27, 2026