Compress images online and keep them private

Image compression explained: balancing quality and file size

Image compression reduces file size by removing redundant or less-important data from the pixel stream. Lossy compression (used by JPG and WEBP) discards information the human eye is less sensitive to — subtle color variations, high-frequency texture details, and minor tonal differences. The result looks nearly identical to the original but can be 60-90% smaller.

The quality slider controls how aggressively the encoder discards data. At quality 90-95, differences from the original are invisible to most viewers. At 70-80, you might notice slight softening in detailed textures but the image still looks professional. Below 50, artifacts become visible — blocky patterns in gradients and smearing around sharp edges.

For web delivery, the sweet spot is usually 75-85 quality. This produces files small enough for fast page loads while maintaining visual quality that satisfies viewers. Google's Core Web Vitals penalize pages with large images that delay Largest Contentful Paint, so compression directly impacts your search ranking.

PNG compression is lossless — it reduces file size through pattern recognition (like ZIP) without discarding any pixel data. PNG files are always larger than equivalent JPG files for photographs, but they preserve every detail perfectly. Use PNG when you need exact pixel reproduction (screenshots, diagrams, logos) and JPG/WEBP when you need small files for web delivery.

Common use cases

• Website speed optimization: Compress hero images, product photos, and blog graphics to reduce page weight by 50-80%, directly improving Core Web Vitals scores and Google search rankings.
• Email newsletter images: Shrink images below email size limits and ensure fast rendering in email clients, where large images often get clipped or blocked by default.
• Mobile app asset preparation: Reduce image assets for mobile apps where download size affects install rates and storage usage on users' devices.
• Cloud storage cost reduction: Compress photo archives before uploading to cloud storage services, reducing storage costs and sync times without losing meaningful visual quality.

Technical details

Compression algorithm

JPG uses DCT (Discrete Cosine Transform) to convert spatial data into frequency components, then quantizes high-frequency details. WEBP uses a similar approach with better entropy coding for smaller files.

Quality scale

The slider maps to the browser's Canvas toBlob() quality parameter (0.0 to 1.0). A value of 0.75 means the encoder targets 75% quality, which typically produces 60-70% file size reduction for photographs.

Per-file savings

The tool shows original size, compressed size, and percentage saved for each file before you download. This lets you verify the trade-off is acceptable before committing.

Batch processing

All files in the batch use the same quality setting. The ZIP download contains every compressed file with a -compressed suffix added to the original filename.

How to compress an image online

Reduce file size while controlling quality, then download the optimized files.

1. Drop images into the compressor or pick them from your device.
2. Adjust the quality slider to balance size and visual fidelity.
3. Review the savings preview for each image.
4. Download the compressed file or grab the whole batch as a ZIP.

Frequently asked questions