Skip to main content

image-compressor

Image compression reduces file size without (or with minimally noticeable) loss in visual quality, by stripping metadata, re-encoding with better compression parameters, or downsampling pixel data. The ZTools Image Compressor does all three on JPG, PNG, and WebP files — entirely in your browser using <canvas> re-encoding plus the browser's native PNG/WebP encoders. Typical results: JPGs shrink 40–70% at quality 80 (visually lossless for most photos), PNGs shrink 15–40% lossless via metadata stripping, WebP often beats both at the same quality. No upload, no queue, no file size limit beyond browser memory.

Use cases​

Optimizing images for web performance​

Hero images, product photos, blog post images — these are typically the biggest contributors to slow page loads. Drop a 4 MB camera JPG in here, compress to quality 80, get a 600 KB output that looks identical to the human eye. Multiply across a site and the LCP improvement is dramatic.

Fitting images into email or upload size limits​

Gmail caps attachments at 25 MB; many forms cap at 5 MB. A camera JPG often exceeds these. Compress before attaching to keep recipients happy and avoid the "your file is too large" form rejection.

Preparing images for mobile apps with strict bundle sizes​

iOS and Android bundle size affects download speed and store ranking. Convert in-app graphics to WebP (smaller than PNG) and compress aggressively. Our tool handles transparency correctly — alpha channel preserved on WebP output.

Stripping EXIF metadata before sharing publicly​

Camera photos contain EXIF data that may include GPS coordinates of where the photo was taken. Re-encoding through our tool strips all EXIF by default, preserving only the pixel data — important when posting photos publicly or sending to people you don't fully trust.

How it works​

  1. Drop or select images — Single file or batch up to 50 at once. Supported: JPG, PNG, WebP, BMP, GIF (first frame only). Max single-file size depends on browser memory; roughly ~50 MP works on most desktops.
  2. Pick output format and quality — Same format (recompress with new params), or convert (e.g., JPG→WebP for smaller output). Quality slider 0–100; 75–85 is the visually-lossless sweet spot for JPG.
  3. Optional resize — Specify max width or height in pixels. Aspect ratio preserved. Common targets: 1920px for web, 1080px for mobile, 800px for thumbnails.
  4. Click Compress — For each image: decode pixels via <canvas>, optionally resize via canvas drawing, re-encode with canvas.toBlob(quality) for JPG/WebP or via PNG encoder for PNG. EXIF is dropped because canvas doesn't carry it.
  5. Preview and download — Side-by-side before/after with file size comparison. Download single or as a ZIP for the batch.

Examples​

Input: Camera JPG, 4032×3024, 4.2 MB

Output: Quality 80 JPG, 4032×3024, 1.1 MB (74% reduction)

Input: PNG screenshot, 2560×1440, 1.8 MB

Output: WebP quality 85, 2560×1440, 220 KB (88% reduction)

Frequently asked questions​

Does compression lose quality?

JPG and WebP at quality < 100 lose information (lossy). At quality 80–85 the loss is invisible to nearly everyone except in smooth gradients. PNG can be re-encoded losslessly (no quality loss, only metadata removal and encoder optimization), typically saving 15–40%.

What is the best format for photos?

WebP if you can use it (~95% browser support since 2020). JPG if you need universal compatibility. PNG only when you need transparency or pixel-perfect lossless. Avoid GIF unless animation is required.

Are my images uploaded to a server?

No. The entire pipeline runs in your browser via Canvas + Blob APIs. Open DevTools → Network and confirm zero requests during compression. Critical for sensitive images (screenshots of dashboards, photos of documents).

Why is my compressed PNG barely smaller?

PNG is already losslessly compressed by its encoder. Our tool re-encodes with optimal settings and strips metadata, but if your input is already well-optimized (e.g., a previously-compressed PNG), additional savings are small. Convert to WebP for major savings.

Can I batch-compress 100 images?

Yes, up to 50 simultaneous. For more, run in batches — browser memory becomes the bottleneck. Each image is processed sequentially, so 50 images take roughly 50× one image's time.

Does it preserve transparency?

Yes when output format supports it (PNG, WebP). JPG does not support transparency, so JPG output of a transparent PNG fills with white (or your specified background color).

Tips​

  • For web use, default to WebP at quality 80 — typically 60–80% smaller than equivalent JPG with no visible quality loss.
  • Always preview the compressed image at 100% zoom before deploying. Quality artifacts hide at thumbnail size.
  • Resize before compressing when possible — a 4032×3024 image scaled to 1920×1440 saves more than any quality reduction would.
  • Strip EXIF before posting any photo publicly. Even Instagram doesn't fully strip GPS data.

Try it now​

The full image-compressor runs in your browser at https://ztools.zaions.com/image-compressor — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub