When examining ICO vs. PNG, we established that individuals might encounter critical decisions on creating, converting, or storing images as ICOs or PNGs. ICO is a popular vector-based format, while PNG is a pixel-based (raster) image file type used on websites, each with its cons and pros.
As such, the article helps you learn when to use and not to use each file type by highlighting and discussing the differences and similarities between ICOs and PNGs in terms of structure, compression, storage, file size, image quality, performance, browser support, animation, and transparency support.
When is PNG better than ICO?
PNG images are detailed and retain image quality with lossless compression, while an ICO image is less detailed and larger than a PNG image, leading to reduced web responsiveness.
A PNG image supports more color bands than an ICO, making it suitable for web illustrations, charts, logos, and graphics because of its stunning visual appeal, quality, and universal browser support.
When is ICO better than PNG?
ICO images are scalable without losing quality and retain their resolution level, while PNG images become blurry or distinct when scaled up or down because of their raster graphic nature. Hence, ICO images are suitable for generating visually attractive desktop shortcuts, website favicons, and application icons.
The pros of ICO images include their ability to be scaled up or down while ensuring image quality and flexibility. They integrate multiple images with different sizes and varying color depths, giving rise to detectible and visually attractive favicons or icons.
ICO versus PNG Table Comparison
| Element | ICO | PNG |
| Transparency | Supports alpha channel transparency | Supports alpha channel transparency |
| File Size | Larger than PNG | Smaller than ICO |
| Image Quality | Limited color support, but scalable up/down without losing quality - high-quality images. | Detailed and high-quality lossless images with notable crispiness and acuity. |
| Performance | Larger multi-level icons than PNG, more bandwidth, and hence load slower. | Smaller than ICO, it has less bandwidth and loads faster. |
| Structure | It has an Icon directory (ICONDIR) linking a block, the AND bitmap, the XOR bitmap, and an image mask. | Has an 8-byte signature header integrating numerous chunks with interior fields subject to the chunk type. |
| Animation | Supports animation or favicons | It does not support animation or lively content |
| Storage | Larger icons or multilayer images require more storage space than PNG. | Lossless PNG images require less storage space than multilayer ICO images. |
| Compression | Uses PNGOUT or TinyPNG lossless techniques | Uses lossless compression with Huffman coding and LZ77. |
| Browser Support | Enjoy limited support from top browsers but unsupported by Older browsers like IE. | Supported by almost all browsers except IE6. |
Differences and similarities between PNG and ICO images
PNG and ICO are versatile file types with similarities in transparency support, browser support, lossless compression, and image quality.
On the other hand, PNG differs from ICO in file size, web performance, structure, animation support, and storage. A tabular comparison of ICO versus PNG can highlight these file formats' key differences and similarities.
Transparency
PNG and ICO file formats support alpha channel transparency. For instance, an ICO image or file supports transparency by allowing developers to add semi-transparent areas, including glass-like effects, anti-aliasing, and shadows to an image. An ICO file format supports 8 bits of transparency.
Conversely, the PNG alpha channel establishes each pixel’s transparency levels, which range from transparent to opaque, as denoted by 0 and 255, respectively. The PNG’s tRNS ancillary chunk then controls the transparent structure.
File Size
Lossless ICO files or images are larger than lossless PNG files or images. An ICO type comprises multiple files or image icons with different sizes and color depths, resulting in larger file sizes. A PNG file has no size limit. However, the maximum file dimension is 2G x 2G pixels.
While raster-based PNG files are not scalable, ICO file sizes can be significantly increased or reduced through up or down scaling to optimally fit screen sizes without losing quality or resolution levels. Each ICO file stores images of varying sizes and types, starting from 1x1 pixel to 256x256 pixels.
The smallest icon in an ICO file has 1 pixel, a medium icon is 48 pixels, a large icon is 96 pixels, and an extra-large icon contains 256 pixels. Thus, multiple ICO files pooled and stored together can be significantly larger than 140 GB or even larger PNG files.
Huffman’s lossless compression algorithms reduce PNG file sizes, and the PNGOUT or TinyPNG algorithms compress ICO files, resulting in file sizes similar to the original ones. The losslessly compressed ICO (PNGOUT) file is nearly an exact image but larger than a lossless PNG.
Image Quality
ICO and PNG are high-quality and high-resolution file formats. Nonetheless, the ICO format has a limited color depth compared to PNG. The ICO format supports a maximum color depth of 24-bit, allowing up to 16 million colors.
Although ICO’s color depth is adequate for designing most icons or favicons, more is needed to create photorealistic or highly detailed icons. In such instances, webmasters or designers may be compelled to use the PNG image format with a higher color depth.
Lossless PNG is a high-quality file format that supports 24-bit RGB or 32-bit RGBA color space, making its quality standard far better than the ICO format. It supports 256 quantized palette colors, even though its TrueColor file supports 16 million colors, as with ICO.
Performance
ICO files are relatively larger than PNG files. The vector-based file format (ICO) can hold multiple images or files of varying color depths and sizes compared to the pixel-based or bitmapped PNG files, increasing its general file size.
While the ICO's larger file size might hardly be a significant factor in considering separate icons, it becomes a concern when users, including webmasters, browsers, or web designers, deal with large numbers of icons, as it can lead to increased bandwidth requirements and prolonged web loading times.
As a result, whereas lossless PNG files are larger but smaller than ICO files, they reduce website loading times compared to ICO files or images. Hence, PNG has a better user experience and optimized search engine than ICO.
Structure
An ICO file is a raster graphics file format, while a PNG file is a raster-based or bitmapped format. ICO file icons can be displayed at different predefined sizes without losing image quality, as they contain multiple versions of the icon at various resolutions. In contrast, a PNG file with a fixed number of pixels becomes pixelated when scaled up beyond its original resolution.
The ICO file structure comprises an Icon Directory (ICONDIR) containing the ICONDIRENTRY header for each image in the file. Following the header is a block with image bitmap data for each image. The ICO file format may include an AND bitmap and the actual icon image data stored in either PNG or Windows BMP format. When the BMP format is used, the BITMAPFILEHEADER structure is excluded. ICO files can contain multiple images with different color depths and sizes to accommodate various display requirements.
The multiple sizes of an ICO file allow for smooth scalability across predefined icon dimensions. On the other hand, PNG has a fixed number of pixels and features two-dimensional interlacing, cross-platform image brightness control, and variable transparency (alpha channel). Scaling a PNG image up results in pixelation and loss of quality due to its fixed resolution.
A PNG file structure begins with an 8-byte signature, followed by chunks containing uniform syntax. The multiple IDAT chunks within a PNG file contain compressed image data stored using the lossless DEFLATE compression algorithm. Each chunk adheres to a specific structure, and its identification corresponds to its content and purpose.
PNG chunks are read sequentially from the start to the end of the data stream. Critical chunks in a PNG file, such as IHDR, IDAT, and IEND, must be supported by any software that reads or writes PNG files. As a result, the structural makeup of ICO and PNG files differs significantly, making direct comparisons between the two formats challenging.
Animation
ICO files support animation, while a PNG file does not. An ICO file supports animation through its icon features, which allow websites or computer applications to be enhanced and customized to support multiple color depths and varying resolution levels.
While PNG files do not support animations, their specifications can be extended in APNG file format, which supports animation by incorporating the animation control chunk. However, animated PNGs are smaller, richer in color, and more appealing than animated ICOs.
Storage
Lossless PNG files are smaller than ICO files, requiring less storage space. However, ICO files are stored in icons for programs, files, and folders. The stored ICO data are encrypted to safeguard against unsanctioned processing or access.
In contrast, the Huffman coding algorithms losslessly compress PNG files, preserving all file details and making them larger but comparatively smaller than PNGOUT-compressed ICO files. Thus, the compressed PNG files necessitate less bandwidth than lossless ICO files.
PNG and ICO files can be stored forever, depending on the storage medium used, the conditions they are subjected to, and the handling process. When properly handled and stored, they can indefinitely retain their colors, forms, shapes, and sizes.
Lossless ICO files are stored in icon directories, including folders, files, or programs. On the other hand, lossless PNG files can be stored indefinitely in the cloud, Base64 encoding, file systems, and Content Delivery Networks.
Compression
The ICO and PNG file formats use lossless compression. However, PNGOUT or TinyPNG lossless compression can compress an ICO image format. While ICO compression is unnecessary (when the images inside the ICO file are stored in the BMP format), Windows recommends compressing ICO images of 256x256 pixels as PNGs.
The ICO file’s performance is optimized when compressed and stored in PNG format. The TinyPNG or PNGOUT algorithms compress the file and ensure the resultant file is small and of higher quality, but it is significantly larger than the compressed PNG.
PNG compresses images using a non-patented lossless compression called DEFLATE. DEFLATE uses different compression algorithms, ranging from 0 (not compressed) to 9 (fully compressed). The PHP GD default application selects the algorithms that combine Huffman coding and LZ77.
The selected algorithms recreate the original image precisely. However, the PNG compression process occurs in two phases: filtering and compression. In the filtering process, delta encoding is used for every scan line of pixels.
The pixels are programmed based on the pixels above the left, the pixels above, and the pixels to the left. The resultant PNG file is passed to DEFLATE, which combines Huffman coding with the LZ77 algorithm. The DEFLATE compression results in the compressed PNG image file.
Browser Support
Only 0.2% of websites use the ICO format, which is 0.6% popular among the top 1 million website browsers. Although it has existed for almost four decades, unlike ICO, PNG is extensively supported and recognized across multiple applications and browsing platforms.
Currently, 81.8% of websites use and support PNG files. Compared to ICO, the file format is widely supported by websites and browsers such as Safari, Discord, Brave, Google, Opera, Instagram.com, Yahoo.com, Whatsapp.com, Edge, and Cloudflare.com, among others.
In contrast, ICO is supported by Opera, Edge, Chrome, and Firefox but not by Internet Explorer and is partially supported by Safari. Its popularity rating is comparable to PNG's because ICO is uncommon in most file stores, while PNG is readily accessible and easy to work with.
Converting PNG to ICO or ICO to PNG
Webmasters or designers may convert PNG to ICO because ICO files are flexible, support animation, and have scalable icons that can be displayed without losing quality compared to PNG. This makes ICO an inventive file format choice for icon imagery. Use Converjack to convert PNG to ICO effortlessly.
On the other hand, users would want to use an ICO to PNG converter known as Convertjack to convert their ICO files to PNG because PNG files support transparency and comprise enriched solid colors and sharp edges, making them perfect for editable images with texts, line art, and graphics.