How to use Compress Image
Reduce image file size by up to 90% without perceptible quality loss — all processing happens in your browser using WebAssembly-powered compression. Supports JPEG, PNG, WebP, and AVIF. Batch-compress multiple images at once, compare before/after quality side by side, and download the optimized files instantly. Smaller images load faster, rank better in Core Web Vitals, and save storage costs.
- Upload one or more images by clicking or dragging them to the tool.
- Select the output format: same as input, JPEG, WebP, or AVIF.
- Choose "By target size" and enter a KB limit, or "By quality" and set the slider (80–85% suits JPEG; 90% WebP).
- Review the before/after comparison and compressed file size.
- Download individual files or all compressed images as a ZIP archive.
Your data never leaves your device — 100% private processing.
Choosing the right output format
JPEG is widely supported and best for photographs — use 75–85% quality for web. PNG is lossless and ideal for screenshots, UI graphics, and images with transparency. WebP produces 25–35% smaller files than JPEG at equivalent quality and is supported in all modern browsers (Chrome, Firefox, Safari, Edge). AVIF is the newest format — 50% smaller than JPEG — but has slightly wider browser support gaps. For 2024 web deployments, WebP is the best balance of compression and compatibility.
| Format | Best for | Compression type | Transparency |
|---|---|---|---|
| JPEG | Photos, complex images | Lossy | No |
| PNG | Screenshots, UI, logos | Lossless | Yes |
| WebP | Web photos and graphics | Lossy or lossless | Yes |
| AVIF | Next-gen web images | Lossy or lossless | Yes |
Quality settings and Core Web Vitals
Google's Largest Contentful Paint (LCP) and Total Blocking Time are directly affected by hero image file size. A 5 MB hero image can fail the LCP threshold (2.5 seconds on a 4G connection) even before JavaScript loads. Compressing the same image to 150–300 KB with WebP typically cuts LCP by 1–2 seconds. The Google Lighthouse "Serve images in next-gen formats" audit specifically recommends WebP and AVIF over JPEG for web content. Aim for hero images under 200 KB and secondary images under 100 KB.
Batch compression workflow
Upload multiple images simultaneously and set a global quality target. Files are processed in parallel using Web Workers, keeping the UI responsive even for large batches. After processing, individual files show their compression ratio and final size. Download a ZIP containing all compressed files with the same names as inputs. For web projects, re-upload the ZIP contents directly to your asset folder — no manual renaming required.
Worked examples
Typical web photo
Inputs: 8 MB JPEG photo at quality 75
Result: Typically 1.5–2.5 MB — varies by image content
Screenshot to WebP
Inputs: 1.2 MB PNG UI screenshot → lossless WebP
Result: Often 300–600 KB — content-dependent
JPEG quality level guide
| Quality | Visual result | Best for |
|---|---|---|
| 90–100% | Near-lossless, large files | Archiving, print masters |
| 80–85% | No visible loss for most photos | Web photos, general use |
| 70–75% | Minor artefacts in fine detail | Thumbnails, email attachments |
| 50–60% | Visible blocking on gradients | Maximum size reduction |
Glossary
- Lossy compression
- A compression method that permanently discards some image data to achieve smaller files, with a slight quality reduction.
- Lossless compression
- A method that reduces file size without discarding any image data — the original can be perfectly reconstructed.
- WebP
- A modern image format developed by Google offering superior compression to both JPEG and PNG with transparency support.
- Core Web Vitals
- Google's metrics for page experience (LCP, INP, CLS) used as ranking signals in search results.
Related reading
Frequently Asked Questions
Why use Compress Image?
- Compress to an exact target size — enter a KB limit (e.g. under 100 KB) and it hits it automatically
- Or use the quality slider to shrink JPEG, PNG, and WebP while preserving visual sharpness
- Batch-compress an entire folder of product photos in a single drag-and-drop session
- Side-by-side before/after preview lets you confirm acceptable quality before downloading
- Smaller images directly improve Google Core Web Vitals LCP scores on your website
Common use cases
- Compress hero images to under 200 KB to pass a Lighthouse performance audit
- Shrink a 5 MB phone photo to meet a job-portal CV attachment size limit
- Reduce a batch of blog post images before uploading them to a CMS
- Compress WebP product thumbnails to speed up an e-commerce category page load
- Lower an email attachment size so scanned receipts fit inside a 25 MB Gmail limit
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