Image Compression & Conversion: WebP, JPEG, and PNG Explained
Images account for 50–80% of a typical webpage's total file size. Choosing the right format and compression level is one of the most impactful performance optimizations you can make — directly affecting Core Web Vitals, page speed scores, and ultimately your Google rankings. Our free tool runs entirely in your browser using the Canvas API, so no image ever leaves your device.
WebP: The Modern Web Standard
WebP was developed by Google and is now supported by all modern browsers (Chrome, Firefox, Safari 14+, Edge). It delivers significantly smaller file sizes compared to JPEG and PNG while maintaining comparable or better visual quality. For photographs and complex images, WebP with lossy compression typically saves 25–35% over JPEG at the same quality level. For images with transparency, it outperforms PNG by an even wider margin — often 50% or more.
When to use WebP
- All web images where browser compatibility with modern browsers is sufficient
- Product images in e-commerce shops
- Blog post hero images and article thumbnails
- Images that need transparency (replaces PNG)
- When you need the smallest possible file size without visible quality loss
JPEG vs PNG: When to Use Which Format
- · Photographs and complex images with gradients
- · Images where small transparency areas don't matter
- · When maximum compatibility is needed (old browsers, email clients)
- · Background images with many colors
Lossy compression — small quality loss acceptable
- · Logos, icons, and illustrations with sharp edges
- · Screenshots and UI elements
- · Images that require full transparency (alpha channel)
- · Images with text that must remain pixel-sharp
Lossless — no quality loss, but larger files
How Compression Quality Affects File Size
The quality slider controls the trade-off between visual quality and file size. A quality setting of 80 is the industry-standard "sweet spot" — files are roughly 60–70% smaller than the original while the quality loss is imperceptible to the human eye. For most web use cases, quality settings between 70–85 are optimal.
Maximum
90–100
Near-lossless, large files
High
75–89
Best for web (recommended)
Medium
50–74
Good compression, slight loss
Low
1–49
Highest savings, visible artifacts
Why Image Optimization Matters for SEO
Google's Core Web Vitals include Largest Contentful Paint (LCP) — which measures how quickly the main image on a page loads. Unoptimized images are the #1 cause of poor LCP scores. By converting images to WebP and compressing them appropriately, you can dramatically improve your page speed, which directly influences Google rankings and user experience metrics.
LCP improvement
Smaller images load faster, improving your Largest Contentful Paint score — one of Google's top 3 ranking signals.
Bandwidth savings
Visitors on mobile connections benefit most. Faster loads mean lower bounce rates and more conversions.
Server costs
Smaller image files mean less bandwidth consumed — lower hosting costs and faster CDN delivery.
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Frequently Asked Questions
Are my images uploaded to a server?
No. All compression and conversion happens 100% in your browser using the Canvas API. Your images never leave your device and are not stored anywhere. This makes the tool completely private and works even offline.
What is the difference between lossy and lossless compression?
Lossy compression (used by JPEG and WebP lossy mode) reduces file size by permanently discarding some image data. The quality loss is usually imperceptible at settings of 75–85. Lossless compression (PNG and WebP lossless) reduces file size without any quality loss, but results in larger files than lossy compression.
Why does PNG sometimes get larger after conversion?
PNG uses lossless compression, so converting from JPEG (which already throws away data) to PNG will result in a larger file because PNG stores all pixel data perfectly. For photographs, always prefer WebP or JPEG over PNG.
Which quality setting should I use for websites?
For WebP and JPEG, quality 75–85 is the recommended range for web use. At 80 (the default), files are typically 60–70% smaller than the original with no perceptible quality difference. Avoid going below 60 unless thumbnail or preview images are acceptable.