JPG to WebP Converter

What is JPG to WebP Conversion?

JPG to WebP conversion transforms an image from a classic lossy compression format to a modern format developed by Google specifically for web use. This involves not just changing the file extension, but complete re-encoding of graphic data using more efficient compression algorithms.

WebP (pronounced "weppy") was introduced by Google in 2010 as part of a project to speed up the internet. The format is based on the VP8 video codec and was originally designed to replace three formats simultaneously: JPG (photographs), PNG (graphics with transparency), and GIF (animation). Over more than a decade of existence, WebP has become the de facto standard for web images.

The main advantage of WebP is significant file size reduction while maintaining visual quality. According to Google, lossy WebP images are 25-34% smaller than comparable JPGs, and lossless WebP is 26% smaller than PNG. This directly affects page load speed, bandwidth consumption, and user experience.

Technical Differences Between JPG and WebP Formats

Compression Algorithms

JPG uses the DCT (Discrete Cosine Transform) algorithm, developed in the late 1980s. The image is divided into 8×8 pixel blocks, each block is transformed into the frequency domain, after which high-frequency components are quantized (rounded), leading to information loss. At high compression levels, characteristic "blocky" artifacts appear at 8×8 block boundaries.

WebP lossy is based on the VP8 video codec and uses block prediction based on neighboring pixels. The algorithm analyzes already encoded image areas and predicts current block values, recording only the difference between prediction and actual data. Block sizes vary from 4×4 to 16×16 pixels, providing more flexible compression without JPG's characteristic artifacts.

WebP lossless uses a completely different algorithm: pixel prediction, entropy coding, and a dictionary of repeating fragments. This allows compressing images without quality loss more efficiently than PNG.

Characteristic Comparison

*Size relative to JPG at comparable quality

Real Size Reduction Examples

Conversion results for typical images:

These figures show that WebP consistently provides 25-35% savings for most photo types with visually indistinguishable quality.

When is JPG to WebP Conversion Necessary?

Website Optimization

JPG to WebP conversion is especially relevant for website owners striving to improve performance:

• E-commerce stores — hundreds and thousands of product cards with photos. Saving 30% on each image totals terabytes of saved bandwidth and seconds of faster catalog loading.

• News portals — articles with illustrations load faster, which is critical for mobile readers with limited data plans.

• Blogs and content sites — every page contains images, and WebP speeds up content display without losing illustration quality.

• Landing pages — loading speed directly affects conversion. Studies show that a 1-second delay reduces conversion by 7%.

• Galleries and portfolios — photographers and designers can showcase more work with less loading time.

Impact on Core Web Vitals and SEO

Google uses Core Web Vitals metrics as a ranking factor. WebP directly affects two of the three key metrics:

LCP (Largest Contentful Paint) — loading time of the largest visible element on the page. Often this is the hero image. Reducing file size by 30% proportionally speeds up LCP.

CLS (Cumulative Layout Shift) — layout shift during loading. WebP with specified dimensions in HTML prevents content "jumping" just like JPG.

Google PageSpeed Insights recommends using modern image formats (WebP, AVIF) and reduces scores for sites using only JPG. Switching to WebP can add 5-15 points to your performance score.

Bandwidth and Resource Savings

For high-traffic sites, conversion to WebP provides noticeable savings:

• Hosting — smaller data transfer volume reduces load on servers and CDN.
• Mobile users — bandwidth savings especially important for users with metered mobile plans.
• Carbon footprint — less data = less energy for transmission and storage.

Conversion Process: What Happens to the File

Stages of JPG to WebP Transformation

1. JPG decoding — the source file is unpacked, pixel values are restored in YCbCr color space. JPG compression artifacts are already present in the image at this stage.

2. RGB conversion — WebP works with RGB color space (or YUV during encoding). Mathematical color coordinate transformation is performed.

3. Image analysis — the WebP encoder divides the image into macroblocks (16×16 pixels) and selects the optimal prediction method for each.

4. Prediction and encoding — for each block, prediction is calculated based on neighboring pixels, then the difference between prediction and actual data is encoded.

5. Quantization — transformation coefficients are rounded with a given quality level. Higher quality = less rounding = larger file size.

6. Entropy coding — quantized data is compressed using arithmetic coding to minimize file size.

What is Preserved and What Changes

Preserved:

• Visual image quality (with proper settings)
• EXIF metadata (capture date, camera settings, GPS)
• ICC color profile
• Resolution and proportions

Changed:

• File size (reduced by 25-35%)
• Compression structure (DCT → VP8)
• Minor color reproduction differences may occur (different algorithms)

WebP Compatibility with Browsers and Software

Browser Support

As of 2024, WebP is supported by 97%+ of browsers:

Not supported: Internet Explorer (any version), Safari 13 and below.

Operating System Support

• Windows 10/11 — native viewing support through the Photos app
• macOS Big Sur+ — support in Preview and Finder
• Linux — depends on installed libraries, works in most distributions
• iOS 14+ — full support
• Android — native support since Android 4.0

Software

Quality Settings During Conversion

Choosing Quality Level

WebP quality parameter (0-100) affects the balance between file size and visual quality:

• Quality 90-100 — minimal compression, practically identical to original. 10-20% savings relative to JPG.
• Quality 75-85 — optimal balance for most tasks. 25-35% savings, artifacts invisible on typical monitors.
• Quality 60-75 — noticeable compression, suitable for thumbnails and previews. 40-50% savings.
• Quality below 60 — strong artifacts, only for special cases.

Recommendation: for websites, optimal quality is 75-82. This provides the best size-to-quality ratio.

Lossy vs Lossless

For photographs (JPG source), WebP lossy is almost always preferable:

• JPG already contains compression artifacts, lossless doesn't make sense
• Lossy WebP is significantly more compact
• Visual difference is invisible

WebP lossless should only be used when converting from PNG or for graphics with text and sharp lines.

WebP vs AVIF: What to Choose

AVIF is an even newer format (2019), providing better compression but with limited support:

Recommendation: for maximum compatibility, use WebP. For cutting-edge projects with modern audiences, consider AVIF with fallback to WebP and JPG.

Implementing WebP on Websites

HTML picture Tag

To support older browsers, use the picture tag with fallback:

<picture>
  <source srcset="image.webp" type="image/webp">
  <source srcset="image.jpg" type="image/jpeg">
  <img src="image.jpg" alt="Description">
</picture>

The browser will choose the first supported format.

Server-Side Delivery by Accept Header

Modern CDNs and web servers can automatically serve WebP to browsers that support it based on the Accept header. This allows storing both formats and serving the optimal one.

CMS and Plugins

Most modern CMS support WebP:

• WordPress — natively since 5.8, plugins ShortPixel, Imagify, Smush
• Drupal — WebP module
• Tilda, Wix, Squarespace — automatic conversion

WebP Format Limitations

When WebP is Not Suitable

• Professional printing — use TIFF or original RAW files for print production
• Archival storage — WebP is not ISO standardized, PNG or TIFF is preferred for long-term storage
• Legacy systems — if your audience uses IE or old Safari versions, fallback is needed
• HDR content — WebP doesn't support extended dynamic range (use AVIF or JPEG XL)

Conversion Considerations

• Original JPG artifacts will remain in WebP — conversion doesn't restore lost data
• File size doesn't always decrease — for very small images (<1 KB) or already optimized JPGs, the difference may be minimal
• Some CMS and forums don't accept WebP — check platform requirements