WebP images: A complete guide for the WebP file format

The WebP format, developed by Google, is a modern image format that provides superior lossless and lossy compression for images on the web. Using WebP, webmasters and web developers can create smaller, richer images that make the web faster. Google introduced the WebP image format in 2010 as part of their mission to make the web faster and more efficient.

When to Use WebP

WebP is a powerful image format, offering distinct advantages in various scenarios. Here are some situations when using WebP is advantageous:

1. Web Images: WebP is specifically designed for the web, offering both lossless and lossy compression. It excels at creating smaller file sizes without compromising image quality, making it ideal for web developers looking to speed up their sites.
2. Transparency and Animation: Unlike JPG, WebP supports transparency, similar to PNG files, and animation, similar to GIF files. This makes it a versatile choice for web designers and developers.
3. Large Image Galleries: Like JPG, using WebP can significantly reduce the storage space required for large collections of images without significant loss of quality.
4. Social Media and Online Platforms: Many platforms, including Google's own services like Google Play Store and YouTube thumbnails, use WebP for efficient loading of images. However, these platforms will seldom (if ever?) ask the user for a WebP-image. How it generally works is that the JPG or PNG that the user feeds in is converted to WebP on upload.

When Not to Use WebP

While WebP is a powerful format, there are specific scenarios where it might not be the best choice. Consider alternative formats in the following situations:

1. Legacy Systems or Certain Browsers: Not all systems or browsers support WebP. If you're targeting a wide range of devices and browsers, including older ones, you might need to provide images in alternative formats as well.
2. Print Production: WebP, like JPG, is primarily designed for digital use. For professional printing, formats like TIFF or RAW are better options as they provide the highest quality and color accuracy.

Optimizing WebP Filesize

For optimizing WebP files, you can use tools like Google's cwebp utility for compressing images into the WebP format. In-depth tips and techniques for reducing image file sizes can be found in our comprehensive guide, How to Reduce Image File Size. This guide covers various methods, including image compression, resolution adjustments, and other helpful tricks to make your WebP files more efficient without compromising on visual appeal.

Frequently asked questions about WebP images

What is WebP?

WebP is an image format developed by Google that provides superior lossless and lossy compression for images on the web. Using WebP, webmasters and web developers can create smaller, richer images that make the web faster.

What is a WebP file?

A WebP file is an image file format that uses both lossy and lossless compression. Developed by Google, WebP is designed to create smaller file sizes that still maintain high image quality. The format is widely supported across modern web browsers, making it a popular choice for web developers seeking to optimize their websites' loading speed and performance.

What does WebP stand for?

WebP doesn't stand for anything. It is simply the name given to the image format developed by Google. The name itself could be thought of as a nod to its primary use case, as it's primarily used for images on the web. The 'P' could also be interpreted as standing for "picture".

How to convert WebP to PNG?

You can convert WebP files to PNG using online converters or image editing software that supports the WebP format. Here are the steps for two popular online converters:

Using Photopea:

1. Open Photopea in your web browser.
2. Go to "File" > "Open", and select your WebP image.
3. Once the image is loaded, go to "File" > "Export As" > "PNG".
4. Finally, click "Save" to download your PNG image.

Using Canva's image converter:

1. Open Canva's image converter in your web browser.
2. Click "Choose a file" and select your WebP image.
3. Choose "PNG" as the output format.
4. Finally, click "Download" to get your PNG image.

Remember to check the converted image for any loss in quality or unwanted changes.

How to convert PNG to WebP?

Use an online converter or image editor that supports PNG to WebP conversion, such as Google's cwebp utility. Upload the PNG file, select "WebP" as the output format, and convert the image.

How to convert WebP to JPG?

Use an online converter or image editor like Photopea, or Canva's free image converter that supports WebP to JPG conversion. Upload the WebP file, select "JPG" as the output format, and convert the image.

How to save a picture as a WebP?

• On PC or Mac: Use your preferred image editor and select "WebP" as the output format when saving the image.
• Online: Use online converters or image editors that support conversion to WebP.

How to view WebP files?

• In Browsers: Most modern web browsers, including Google Chrome, Firefox, and Edge, support viewing WebP files.
• Image Viewers: Some image viewers, such as IrfanView and XnView, support WebP files.
• Online: You can also use online image editors or viewers to open WebP files.

How to reduce the size of a WebP file?

Use an image compression tool or software that supports WebP, such as Google's cwebp utility, to adjust the quality or resolution of the WebP image. This guide on how to reduce image file size offers more ways to reduce the size of your WebP files.

How to edit a WebP?

Open the WebP file in an image editing software that supports the format, such as GIMP, Paint.NET, or Photopea. Edit the image as desired, then save the changes.

Tools for Working with WebP Files

Image Editors for WebP

• Adobe Photoshop: This popular image editing software supports WebP with the use of plugins.
• GIMP: A free, open-source image editor that natively supports WebP files.
• Photopea: An online image editor that supports various formats, including WebP.

Conversion Tools for WebP

• cwebp: Google's own command line tool to convert images to WebP format.
• Ezgif's WebP Converter: An online converter that allows for easy conversion between WebP and various other formats.
• Online-Convert: A comprehensive online converter that supports conversion to and from WebP format.

Compression Tools for WebP

• cwebp: Google's command line tool offers options to adjust the level of compression in WebP files.
• Ezgif's WebP Optimizer: An online tool for optimizing and compressing WebP files.

How The WebP Format Compresses Your Image

For those passionate about understanding image file formats and their inner workings, here is a deep dive into the WebP format and how it achieves its impressive compression:

WebP employs two types of sophisticated algorithms to achieve significant image compression while maintaining acceptable visual quality. These are the Lossless and Lossy compression modes. Let's break down the essential steps in the WebP compression process:

1. Predictive Coding: The compression process in WebP begins with predictive coding. WebP uses a technique called 'intra-frame prediction' to guess the color of a pixel based on the pixels around it. This is done for blocks of pixels within the image. The prediction error (the difference between the actual and predicted pixel values) is then stored instead of the original pixel values, as it's typically smaller and thus easier to compress.
2. Transform Coding: The prediction errors are then subjected to a process known as transform coding. Transform coding involves the use of a mathematical function to convert the error data into a different format that can be more effectively compressed.
3. Entropy Coding: After transform coding, the data is encoded using an entropy coding algorithm. This is essentially a form of lossless compression that utilizes the statistical nature of the information to further reduce the data size. WebP uses the VP8 format for entropy coding in lossy images and a variant of the LZ77 and Huffman coding in lossless images.
4. Chroma Subsampling: In its lossy compression mode, WebP also utilizes a technique called chroma subsampling. Chroma subsampling is a method that reduces the color information in an image in favor of preserving detail and brightness, thereby decreasing file size.

Adjusting the Level of Compression in WebP

Controlling the degree of compression in WebP files provides flexibility to balance between the file size and image quality, making it suitable for various applications. Here's how you can adjust the compression level:

WebP compression level can be managed during the encoding process. Most image editing and conversion tools that support WebP provide an interface or setting to adjust the compression. Typically, the quality level can be set on a scale from 0 to 100, with 100 providing the best image quality and 0 the highest compression.

The compression level in WebP directly influences the file size and the quality of the image. Lower values result in higher compression but lower image quality due to the lossy nature of the compression. Higher values will give better image quality at the cost of larger file sizes.

Here are a few guidelines to help you choose the right compression level:

• High-Quality Images: If you're dealing with images that need to maintain high visual quality, such as professional photography, digital art, or high-definition graphics, you'll want to opt for a higher compression level, typically 80-100. These values will result in larger file sizes, but the image quality will be maintained.
• General Purpose Images: For general purpose use, such as web graphics, blog images, or social media posts, a balance between file size and image quality is often desired. A medium compression level of around 60-80 usually works well for this.
• Low-Quality Images: If file size is your primary concern and image quality is less important, such as for thumbnails, icons, or images intended for fast web loading, you can opt for a lower compression level, typically 0-60.

Remember, the appropriate level of compression is subjective and highly dependent on the specific use case. It's always a good idea to experiment with different levels and visually inspect the results to make your final decision.

Note: While setting compression level, it is important to remember that going beyond a certain point will not yield any further reductions in file size. This is due to the inherent limitations in the compression algorithm.

WebP Compression Quality and Artifacts

Balancing compression level with image quality is crucial when working with WebP. Higher compression levels result in smaller file sizes but also lead to increased image degradation and more visible artifacts. Here are some common artifacts associated with WebP compression:

• Block Artifacts: Just like with the JPEG format, aggressive compression can cause blocky artifacts in areas with abrupt changes in color or brightness. These artifacts are a result of the block processing and quantization.
• Compression Artifacts: Overly compressed images may show compression artifacts, such as "blocking" or "mosquito noise," where small, random squares or distortions appear around edges and fine details.
• Color Banding: Heavy compression can cause color banding, where smooth gradients are reduced to distinct bands of colors, resulting in a loss of color smoothness.

Lossless vs. Lossy Compression

WebP provides both lossless and lossy compression modes, giving it an edge over many other image formats. This means that depending on the use case, you can choose to maintain all image data (lossless) or discard some of it (lossy) to achieve higher levels of compression.

While lossy compression results in significantly smaller file sizes, it is not recommended for situations where image fidelity is critical, such as professional printing or preserving original artwork.

This WebP-guide is part of an article series

If you enjoyed this article, you might also enjoy the other parts of this article series on image file formats: PNG, HEIC, GIF and JPG.