Image compression is a technology that reduces the file size while preserving its visual appearance as much as possible. Photos taken with smartphones or digital cameras can easily exceed several megabytes (MB) in size. By using image compression, you can significantly reduce the file size, making storage, sharing, and web publishing much easier.
Today, compression is used across many image formats, including JPEG, PNG, WebP, AVIF, HEIC, and GIF. Since the compression method, image quality, and file size vary for each image format, it is important to understand their characteristics and use them appropriately.
- What image compression is
- How image file size is reduced
- The difference between lossless and lossy compression
- Why image quality degrades
- What compression ratio means
- Advantages and disadvantages of image compression
- Compression methods for each image format
What Is Image Compression?
Image compression is a technology that reduces the file size while maintaining its quality as much as possible. Photos taken with smartphones or digital cameras can range from several megabytes to tens of megabytes. Compressing images not only saves storage space but also helps improve page load speeds and reduce data consumption.
Today, compression is used across many image formats, including JPEG, PNG, WebP, AVIF, HEIC, and GIF. Since the compression method, image quality, and supported features vary depending on the image format, it is crucial to choose the appropriate format according to your needs.
Why is Image Compression Necessary?
As the resolution of an image file increases, so does its size. Storing large volumes of large image files strains storage space, and sending them via email or social media can take a significant amount of time. Furthermore, on web pages, heavier images result in slower loading speeds, which can lead to user abandonment and lower SEO rankings. Therefore, image compression has become an indispensable technique in modern web production and photography management.
How Image File Size is Reduced
Image compression reduces file size by efficiently organizing or deleting "redundant information" and "information that is barely noticeable to the human eye" within the image data. For example, consecutive sections of the same color can be recorded together, or subtle color information that is difficult for humans to distinguish can be omitted, allowing the file size to be reduced without significantly changing the visual appearance.
There are two main types of compression methods: "Lossless Compression" and "Lossy Compression," each with different characteristics.
What Is Lossless Compression?
Lossless Compression is a compression method that reduces file size without losing any image data. Since the original image can be perfectly restored even after compression, there is no loss of image quality no matter how many times it is saved.
It is suitable for logos, illustrations, screenshots, diagrams, and images containing text, where fine lines and characters need to remain sharp and clear.
Image Formats Using Lossless Compression
- PNG
- GIF
- SVG (during data compression)
- WebP (Lossless mode)
- AVIF (Lossless mode)
- Image quality does not degrade at all
- Can be completely restored to the original image
- Works very well with text and illustrations
- File size tends to be larger for photographs
What Is Lossy Compression?
Lossy Compression is a compression method that significantly reduces file size by deleting portions of image data that are less perceptible to the human eye. While it achieves a much higher compression ratio than lossless compression, the deleted data cannot be recovered.
It is highly efficient for images with a large number of colors, such as photographs, and is widely used in digital cameras and smartphones.
Image Formats Using Lossy Compression
- JPEG
- WebP
- AVIF
- HEIC
Why Image Quality Degrades
Lossy compression reduces size by removing fine color details and noise that are mostly unnoticeable to the human eye. However, if the compression ratio is set too high, artifacts such as block noise, blurriness, and color bleeding may occur, resulting in a noticeable decline in image quality.
Relationship with Compression Ratio
A lower compression ratio maintains high image quality but results in a larger file size. On the other hand, a higher compression level reduces the file size but makes image quality more prone to degradation. It is important to adjust the balance between image quality and file size according to your purpose.
- Achieves an extremely high compression ratio
- Works very well with photographs
- Repeated saving can lead to a decline in image quality
- Widely used on websites and social media
What Is Compression Ratio?
The compression ratio is an indicator of how much an image has been reduced in size. For example, if a 10MB image becomes 2MB, it has been compressed significantly.
Generally, JPEG, WebP, AVIF, and HEIC offer high compression ratios, while PNG and GIF have lower compression ratios as they prioritize image quality.
In recent years, AVIF has gained attention as one of the image formats with the highest compression ratios, and WebP is also widely used across websites.
Advantages and Disadvantages of Image Compression
While image compression offers numerous benefits, there are certain points to be mindful of depending on the method used. Particularly for website administrators, blogs, and e-commerce sites, proper image compression leads to improvements in loading speeds and SEO.
Advantages
- Reduces file size
- Saves storage space
- Improves page load speeds
- Reduces data consumption
- Makes sharing via email and social media easier
- May improve SEO
- Loads quickly even on smartphones
Disadvantages
- Lossy compression may degrade image quality
- Excessive compression ratios cause noise and artifacts
- Supported software varies depending on the image format
- Choosing an unsuitable format can worsen quality or file size
What are the Benefits of Compressing Images?
Saves Storage Space
Compressing images significantly reduces the storage usage on your smartphone or computer. This is especially effective when storing a massive amount of photos or images.
Reduces Data Consumption
As image sizes become smaller, internet data consumption decreases as well. This allows images to load quickly even on mobile network connections.
Improves Website Loading Speeds
Images often account for a major portion of a web page's total size. Compressing images lightens the overall page, leading to faster display times.
Enhances SEO Performance
Google considers page loading speed as one of the ranking factors in its search algorithm. Properly compressing images speeds up page loads, which can positively impact user experience and SEO.
Improves Core Web Vitals
Reducing image sizes also contributes to improving Core Web Vitals, such as LCP (Largest Contentful Paint). The benefits of compression are particularly noticeable for images displayed in the initial view (above the fold).
What Happens If You Over-Compress?
In lossy compression, setting the compression ratio too high will significantly lower the image quality. In particular, the following phenomena can occur with JPEG images:
Block Noise
Square, block-like artifacts may appear across the image. This tends to be highly noticeable in areas like human skin or the sky.
Mosquito Noise
A phenomenon where distortion or haziness appears around text or sharp outlines. This can make fine lines and text difficult to read.
Blurriness
Fine patterns and outlines are lost, giving the entire image a blurry or fuzzy impression.
Color Bleeding & Banding
Gradients in areas like the sky or sunsets become unnatural, making the boundaries between colors clearly visible.
- Do not increase the compression ratio more than necessary
- Use JPEG, WebP, or AVIF for photographs
- Use PNG or SVG for logos and text
- Choose the image format that matches your purpose
Compression Methods by Image Format
The compression method used varies depending on the image format. It is important to understand what each format excels at and use them accordingly.
| Image Format | Compression Method | Features |
|---|---|---|
| JPEG | Lossy | For photos / High compression |
| PNG | Lossless | No quality loss / Supports transparency |
| GIF | Lossless | Supports animation |
| WebP | Lossless & Lossy | For Web / High compression |
| AVIF | Lossless & Lossy | Next-gen / Excellent compression |
| HEIC | Lossy | Apple's default image format |
| SVG | Vector Format | No degradation when scaled |
Differences Before and After Compression
When you compress an image, the file size can become significantly smaller even if the appearance looks almost identical. With modern image formats, it is not uncommon to reduce the file size by 50% to 80% while maintaining visual quality.
| Status | Size | Quality |
|---|---|---|
| Before Compression | 10MB | ★★★★★ |
| After JPEG Compression | 3MB | ★★★★☆ |
| After WebP Compression | 2MB | ★★★★★ |
| After AVIF Compression | 1.5MB | ★★★★★ |
Compression Ratio Comparison by Image Format
The compression ratio, quality, and ideal use cases vary greatly depending on the image format. It is vital to choose the optimal format for photos, illustrations, or websites.
| Image Format | Compression Method | Quality | Compression Ratio | Photo | Transparency |
|---|---|---|---|---|---|
| AVIF | Lossless / Lossy | ★★★★★ | ★★★★★ | ◎ | ◎ |
| WebP | Lossless / Lossy | ★★★★★ | ★★★★☆ | ◎ | ◎ |
| HEIC | Lossy | ★★★★★ | ★★★★☆ | ◎ | △ |
| JPEG | Lossy | ★★★★☆ | ★★★☆☆ | ◎ | × |
| PNG | Lossless | ★★★★★ | ★★☆☆☆ | △ | ◎ |
| GIF | Lossless | ★★☆☆☆ | ★★☆☆☆ | △ | ◎ |
| SVG | Vector | ★★★★★ | ★★★★★ | × | ◎ |
Recommended Image Formats by Use Case
The optimal image format depends on what you are using it for. You can reference the guide below to make your choice easier.
| Use Case | Recommended Format | Reason |
|---|---|---|
| Photographs | JPEG / WebP / AVIF | Provides high image quality with smaller file sizes. |
| Blogs | WebP | Offers a great balance between loading speed and quality. |
| E-commerce Sites | AVIF / WebP | Improves user experience through faster page loads. |
| Social Media | JPEG / WebP | Supported by most websites and social media platforms. |
| Printing | JPEG / PNG | Allows images to be saved in high quality. |
| Logos & Icons | SVG | Quality does not degrade when zooming or resizing. |
| Illustrations | PNG / SVG | Preserves sharp lines and accurate colors. |
| Screenshots | PNG | Saves text and user interfaces clearly for readability. |
Frequently Asked Questions
What Is image compression?
Image compression is a technology that reduces the file size of an image while preserving its visual appearance as much as possible. It helps save storage space and speed up websites.
What Is lossless compression?
Lossless compression is a method that reduces size without any degradation in image quality. It is used in formats like PNG and GIF.
What Is lossy compression?
Lossy compression is a method that achieves a high compression ratio by removing a portion of the image data. It is used in formats such as JPEG, WebP, AVIF, and HEIC.
Which image format has the highest compression ratio?
Currently, AVIF is one of the image formats with the highest compression ratios. WebP also achieves both high quality and high compression, making it widely used on many websites.
Does compressing an image lower its quality?
With lossless compression, there is no loss of image quality. With lossy compression, the quality may decline if the compression ratio is set too high.
Summary
Image compression is a vital technology that reduces file sizes to save storage space and data consumption, ultimately improving page load speeds. By selecting the appropriate image format for your purpose, you can achieve both high image quality and lightweight file sizes.
- Image compression is a technology to reduce file size
- Lossless compression does not degrade image quality
- Lossy compression can achieve high compression ratios
- JPEG, WebP, and AVIF are recommended for photos
- PNG and SVG are recommended for logos and illustrations
- On websites, image compression leads to improvements in SEO and page load speed
Understanding and using the characteristics of each image format appropriately helps not only save storage space but also maintain smooth website operations and efficient image management.
Related Tools
- Convert Image to JPG : Convert PNG, WebP, AVIF, BMP, etc., to JPG
- Convert Image to PNG : Convert JPG, WebP, AVIF, BMP, etc., to PNG
- Convert Image to WebP : Speed up your site with a next-gen format
- Convert Image to AVIF : Achieve high compression and high quality with a next-gen image format