What is WebP? Complete Guide to Google's Image Format

A Brief History of WebP

WebP was developed by Google and first released in September 2010. It grew out of the VP8 video codec — the same technology behind the WebM video format. Google's motivation was straightforward: images accounted for the majority of web traffic, and existing formats (JPEG and PNG) hadn't seen meaningful compression improvements in years. If Google could make images 25–35% smaller across the web, it would save enormous amounts of bandwidth for both users and its own infrastructure.

Adoption was slow at first. Only Chrome supported WebP for several years, and Safari held out until 2020 (Safari 14, macOS Big Sur). By 2022, every major browser supported the format, and by 2026, global browser support exceeds 97%. WebP has effectively become the de facto standard for modern web images.

How WebP Compression Works

Lossy Mode

WebP's lossy compression is based on the same predictive coding used in VP8 video. The image is divided into blocks (called macroblocks), and each block is predicted from previously decoded blocks using intra-prediction (within the same frame). The prediction error — the difference between the predicted block and the actual block — is then transformed using a DCT-like transform, quantized, and entropy-coded.

The key advantage over JPEG: WebP's block prediction is more sophisticated, which means less information needs to be stored in the residual signal. This is why WebP achieves 25–35% smaller files than JPEG at equivalent visual quality.

Lossless Mode

WebP lossless uses a completely different algorithm from its lossy mode. It employs several techniques:

Spatial prediction — Pixels are predicted from their neighbors, and only the prediction error is stored.
Color transform — The image is converted from RGB to a decorrelated color space that compresses better.
Subtract Green transform — Exploits the fact that the green channel in natural images carries the most information, using it to predict the other channels.
LZ77 backward references — Repeated patterns in the image are referenced instead of stored twice.
Huffman coding — The final bitstream uses Huffman entropy coding for compact representation.

WebP lossless files are typically 25–35% smaller than equivalent PNGs.

Alpha Channel (Transparency)

Unlike JPEG, WebP supports an alpha channel for transparency in both lossy and lossless modes. In lossy mode, the alpha channel can be compressed losslessly while the color data is compressed lossily — a useful trick that keeps edges sharp while still saving space on the photographic content.

Animation

WebP supports multi-frame animation, similar to GIF but with vastly better compression. An animated WebP file is typically 60–80% smaller than an equivalent GIF, with support for 24-bit color and alpha transparency (GIF is limited to 256 colors).

WebP vs JPEG vs PNG

Feature	JPEG	PNG	WebP
Compression	Lossy only	Lossless only	Lossy + Lossless
Typical file size (photo)	Baseline	5–10× larger	25–35% smaller than JPEG
Transparency	No	Yes	Yes
Animation	No	No (APNG exists but rarely used)	Yes
Color depth	8-bit	8/16-bit	8-bit
Max dimensions	65,535 × 65,535	2,147,483,647 × 2,147,483,647	16,383 × 16,383
Browser support (2026)	100%	100%	97%+
Encoding speed	Very fast	Fast	Fast
Progressive loading	Yes	Yes (interlaced)	No
Metadata (EXIF/XMP)	Yes	Yes (limited)	Yes

Pros and Cons of WebP

Advantages

Smaller files — 25–35% smaller than JPEG for photos, 25–35% smaller than PNG for graphics. This translates directly to faster page loads and lower bandwidth costs.
Versatility — One format handles photos (lossy), graphics (lossless), transparency, and animation. You can replace JPEG, PNG, and GIF with a single format.
Near-universal support — At 97%+ browser coverage, you can use WebP without a fallback for most audiences.
Fast encoding — Unlike AVIF, WebP encodes quickly enough for real-time use (dynamic thumbnail generation, on-the-fly conversion).
Mature ecosystem — Libraries exist for every major language (libwebp, Pillow, Sharp, etc.), and every major CDN can serve WebP automatically.

Limitations

Max resolution of 16,383 × 16,383 — This cap means WebP isn't suitable for very large images like high-resolution maps, gigapixel panoramas, or some medical imaging applications.
No progressive rendering — JPEG can display a low-quality version of the entire image while the rest loads. WebP must be fully downloaded before any part is rendered. For large hero images on slow connections, this can feel slower.
8-bit color only — WebP doesn't support HDR, 10-bit, or 12-bit color. For HDR workflows, AVIF is the better choice.
AVIF is more efficient — AVIF typically produces files 15–25% smaller than WebP at the same quality. If maximum compression is the priority, AVIF wins.
Limited support outside the web — Some desktop applications, printing services, and legacy systems still don't accept WebP. JPEG remains more portable in non-web contexts.

When to Use WebP

WebP is the right choice when you need a practical, well-supported upgrade from JPEG and PNG. Specifically:

Web development — Use WebP as your default image format for websites and web apps. The 25–35% savings over JPEG directly improve Core Web Vitals scores.
Replacing PNG with transparency — If you're serving PNG files with alpha channels (product photos on transparent backgrounds, UI elements), WebP lossy+alpha produces dramatically smaller files.
Replacing GIF — Animated WebP files are 60–80% smaller than GIFs with better color fidelity.
When AVIF is too slow or unsupported — If your workflow requires fast encoding (e.g., real-time thumbnail generation) or you need to support browsers that don't have AVIF yet, WebP is the pragmatic middle ground.

How to Convert Images to WebP

There are multiple ways to convert existing images to WebP:

Using Deflato (Online)

Deflato converts JPEG, PNG, HEIC, AVIF, and other formats to WebP in your browser:

Upload your images (up to 50 at once).
Select WebP as the output format.
Set quality (80 is a good default for photos, lossless for graphics).
Download the converted files.

Using cwebp (Command Line)

Google provides the cwebp command-line tool as part of the libwebp package:

# Lossy compression at quality 80
cwebp -q 80 input.jpg -o output.webp

# Lossless compression
cwebp -lossless input.png -o output.webp

# Batch convert all JPEGs in a directory
for f in *.jpg; do cwebp -q 80 "$f" -o "${f%.jpg}.webp"; done

Using Deflato's API (Programmatic)

For automated pipelines, the Deflato API converts to WebP with a single HTTP call:

curl -X POST https://deflato.com/api/v1/compress   -H "Authorization: Bearer YOUR_API_KEY"   -F "file=@photo.jpg"   -F "output_format=WEBP"   -F "quality=80"   --output photo.webp

Conclusion

WebP is no longer an experimental format — it's the practical standard for web images in 2026. It offers meaningful compression improvements over JPEG and PNG, supports transparency and animation, and works in virtually every browser. While AVIF pushes compression further, WebP's combination of speed, compatibility, and ecosystem maturity makes it the safest default for most projects. If you're still serving JPEG and PNG on the web, switching to WebP is one of the easiest performance wins available.