Image File Formats Explained: The Ultimate Conversion Guide
What You'll Learn in This Guide
This guide breaks down every major image format you'll encounter — from the ubiquitous JPG to next-gen formats like AVIF. You'll understand how compression works, when transparency matters, and which format delivers the best quality-to-size ratio for your specific use case.
Whether you're optimizing images for a website, preparing files for print, or trying to figure out why your iPhone photos won't open on a Windows PC, this guide has you covered. We compare real file sizes, explain the technical tradeoffs in plain language, and link you to free conversion tools throughout.
Understanding Image Formats: Raster vs Vector
Every image format falls into one of two categories: raster or vector. Raster images like JPG, PNG, WebP, and AVIF store color data for each individual pixel in a grid. When you zoom in far enough, you see the individual squares. Vector images like SVG store mathematical instructions — lines, curves, and shapes — that scale to any size without losing quality.
In practice, photos are always raster because camera sensors capture pixel data. Logos, icons, and illustrations are often better as vectors because they stay crisp at any resolution. Understanding this distinction saves you from common mistakes like trying to enlarge a small JPG (it gets blurry) or saving a photograph as SVG (the file becomes enormous with no benefit).
For a deeper comparison of when to use each type, see our guide on SVG vs PNG for web graphics.
Lossy vs Lossless Compression
Compression is how image formats keep file sizes manageable. Lossy compression permanently discards data the human eye is unlikely to notice — subtle color gradations, fine texture details. JPG, WebP in lossy mode, and AVIF all use lossy compression. A typical photo compressed at quality 80 looks nearly identical to the original but is 10 to 20 times smaller.
Lossless compression reduces file size without discarding any data. PNG, TIFF, and WebP in lossless mode use this approach. The file is smaller than the raw data, but every single pixel is preserved exactly. Expect lossless files to be 2 to 5 times larger than their lossy equivalents for the same image.
The right choice depends on your priorities. Publishing photos online? Lossy compression at quality 80-85 is the sweet spot. Archiving original photographs? Lossless preserves your options for future editing. Saving screenshots with text? Lossless prevents the smudgy artifacts that lossy compression creates around sharp edges.
JPG/JPEG — The Universal Photo Format
JPG (also written JPEG — they are the same format) has been the default photo format since 1992. It uses lossy compression based on the discrete cosine transform, which is a fancy way of saying it is very good at compressing photographs. A 24-megapixel camera RAW file at 25 MB compresses to roughly 2-5 MB as a high-quality JPG.
JPG works on literally every device and application ever made. Email clients, web browsers, social media platforms, photo printers — all handle JPG without any conversion needed. That universal compatibility is its greatest strength, even as newer formats offer better compression.
The limitations are real, though. JPG does not support transparency, so you cannot place a JPG logo over a colored background without a visible rectangle. It also degrades each time you re-save it — editing and saving a JPG five times produces noticeably worse quality than the original. For archival work, always keep the original and export JPG copies as needed.
PNG — Lossless Quality with Transparency
PNG was created in 1996 as a patent-free replacement for GIF, and it does far more than its predecessor. PNG uses lossless compression, meaning every pixel is preserved exactly. It supports full alpha transparency — not just on or off, but every level in between — making it essential for logos, UI elements, and graphics that overlay other content.
Screenshots are where PNG really shines. The sharp text and flat colors in a typical screenshot compress efficiently with PNG, often producing files under 500 KB. The same screenshot saved as JPG would show visible artifacts around text edges, even at quality 95.
The downside is file size for photographs. A photo saved as PNG can be 5 to 10 times larger than the same image as a JPG, with no visible quality difference to the naked eye. If you are putting photos on a website, PNG is almost never the right choice — use JPG, WebP, or AVIF instead.
WebP — Google's Modern Web Format
Google introduced WebP in 2010, and by 2026 it has become the web's preferred image format. WebP delivers 25-35% smaller files than JPG at equivalent visual quality. It supports both lossy and lossless compression, transparency, and even animation — essentially combining the best features of JPG, PNG, and GIF into one format.
Browser support is now essentially universal. Chrome, Firefox, Safari, Edge, and every major mobile browser handle WebP natively. The only holdouts are some legacy desktop applications and older image editors. If you are building a website in 2026, WebP should be your default image format.
Converting existing images to WebP is straightforward. Most image editors now export WebP directly, and online tools like iformat.io's WebP converter handle batch conversions in seconds. For a detailed comparison with other next-gen formats, read our AVIF vs WebP vs JPEG XL comparison.
AVIF — The Compression King
AVIF offers the best compression ratios of any widely supported image format in 2026. Based on the AV1 video codec, AVIF produces files that are roughly 50% smaller than JPG and 20% smaller than WebP at the same visual quality. For bandwidth-conscious websites, that is a massive improvement.
AVIF also supports HDR, wide color gamuts, and film grain synthesis — features that matter for high-end photography and display technology. It handles both lossy and lossless compression, supports transparency, and can store animated sequences.
The tradeoff is encoding speed. Compressing an image to AVIF takes significantly longer than JPG or WebP — sometimes 10 to 20 times longer. Browser support has grown rapidly, with Chrome, Firefox, and Safari all supporting AVIF natively. For a deep dive, see our next-gen image format comparison.
HEIC/HEIF — Apple's Default Photo Format
Since iOS 11, every iPhone has captured photos in HEIC by default. HEIC uses the HEVC video codec for still images, achieving roughly 50% smaller files than JPG at equivalent quality. An iPhone photo that would be 4 MB as JPG is typically around 2 MB as HEIC.
The problem is compatibility. Windows added HEIC support via a codec extension, but many web platforms, email clients, and image editors still do not handle HEIC natively. If you need to share photos with non-Apple users, converting to JPG remains the most reliable approach. Use our HEIC to JPG converter for quick batch conversion.
SVG — Scalable Vector Graphics
SVG is fundamentally different from every other format in this guide. Instead of storing pixels, SVG stores XML instructions that describe shapes, paths, and colors. A simple logo might be just 2 KB as an SVG, while a PNG version of the same logo at high resolution could be 50 KB or more.
The killer feature is infinite scalability. An SVG logo looks perfectly crisp whether displayed as a 16-pixel favicon or a 16-foot billboard. You can also style SVGs with CSS and animate them with JavaScript, making them incredibly flexible for web design.
SVG is terrible for photographs, though. Converting a photo to SVG produces either a massive file or a heavily simplified approximation. Keep photos in raster formats and use SVG for graphics with clean lines and flat colors. Learn more in our SVG vs PNG comparison guide.
TIFF — The Professional Print Standard
TIFF is the professional standard for print production, medical imaging, and archival photography. It supports 16-bit and even 32-bit color depth, lossless compression, layers, and multiple pages in a single file. When a print shop asks for high-resolution images, they typically mean TIFF.
The tradeoff is file size. A single TIFF can easily be 50-100 MB for a high-resolution photograph. That makes TIFF impractical for web use or email sharing. Think of TIFF as the archival master copy — you store TIFFs and export JPGs or PNGs for everyday use. Read more in our TIFF vs PNG vs RAW photography guide.
GIF — Animated Images and Memes
GIF has been around since 1987 and refuses to die. Its claim to fame is animation support — those looping clips you see everywhere on social media and messaging apps. GIF is technically limited to 256 colors per frame, which is why GIF animations often look grainy compared to video.
In practice, GIF is being replaced by animated WebP and AVIF, which offer better quality at smaller file sizes with full color support. A 5 MB GIF might be just 1 MB as animated WebP. Still, GIF universal support and cultural momentum keep it relevant — every messaging platform supports inline GIF playback.
BMP — Windows Bitmap
BMP is the original Windows image format, storing pixel data with zero compression. A 1920x1080 screenshot is roughly 6 MB as BMP compared to under 500 KB as PNG. There is almost no reason to use BMP in 2026. If you encounter BMP files, convert them to PNG for lossless quality or JPG for smaller sizes.
ICO — Favicons for Websites
ICO files are special containers that hold multiple sizes of the same image — typically 16x16, 32x32, 48x48, and 256x256 pixels. Browsers use ICO files as favicons, the small icons in browser tabs. While modern browsers also accept PNG and SVG favicons, ICO remains the most universally compatible option.
Creating a proper favicon requires generating multiple sizes and bundling them into a single ICO file. Our complete favicon creation guide walks you through the process step by step, including the specific sizes each browser expects.
RAW — Camera Sensor Data
RAW is not really an image format — it is the unprocessed data captured directly by your camera sensor. Each manufacturer has their own RAW variant: Canon uses CR2/CR3, Nikon uses NEF, Sony uses ARW, and Adobe created DNG as a universal standard. RAW files contain 12-14 bits of color data per channel compared to JPG's 8 bits.
That extra data gives photographers maximum flexibility when editing. You can recover blown-out highlights, lift deep shadows, and adjust white balance after the shot — things that are impossible or destructive with JPG. The tradeoff is file size at 25-75 MB per image and the requirement to process each RAW file before sharing.
For a practical walkthrough of the RAW-to-JPG workflow across camera brands, see our guide on converting RAW photos to JPG.
Quick Format Comparison: Real File Sizes
Here is what happens when you save the same 24-megapixel photograph in different formats. An uncompressed BMP clocks in around 70 MB. TIFF with lossless compression drops to about 35 MB. PNG achieves roughly 20 MB. JPG at quality 85 lands at approximately 3 MB. WebP at equivalent quality hits around 2.2 MB. And AVIF manages roughly 1.8 MB — all with no visible difference to the human eye.
For screenshots and graphics with flat colors, the ranking shifts. PNG often produces smaller files than JPG for this type of content because its compression algorithm is optimized for areas of uniform color. A typical screenshot might be 200 KB as PNG but 350 KB as JPG at quality 95, with the JPG showing visible artifacts around text.
How to Choose the Right Image Format
Choosing an image format comes down to four questions: What is the content? Where will it be displayed? Does it need transparency? And how important is file size? Here is the decision framework that works for most situations.
For web photos, use WebP as your primary format with AVIF as a progressive enhancement. Both deliver excellent quality at small file sizes. For universal compatibility when sharing via email or messaging, JPG is still the safest choice. Every device on earth opens JPG files without issues.
For graphics, logos, and screenshots, use PNG when you need raster output or SVG when vector makes sense. If the graphic needs to overlay other content, you need transparency — which means PNG, WebP, AVIF, or SVG but not JPG. For print production, TIFF provides the quality and color depth that professional workflows demand.
For a more detailed format comparison, see our JPG vs PNG vs WebP vs AVIF comparison guide.
Converting Between Image Formats
Converting between image formats is one of the most common tasks in digital media work. The key principle is that you can always go from a higher-quality format to a lower-quality one without issues, but going the other way has limitations. Converting PNG to JPG works perfectly. Converting JPG to PNG preserves what you have but will not restore data that lossy compression already discarded.
For quick conversions, iformat.io handles all major image formats directly in your browser — no uploads to external servers required. Convert WebP to JPG, HEIC to JPG, AVIF to JPG, SVG to PNG, and dozens of other format pairs instantly.
When converting in bulk for a website, consider automating the process with build tools. Most web frameworks have plugins that automatically generate WebP and AVIF versions of your images during the build step, serving the optimal format to each visitor browser.
Key Takeaways
JPG remains the universal standard for photographs and the safest choice for sharing. PNG is essential for screenshots, graphics with transparency, and any image where lossless quality matters. WebP should be your default for web images in 2026 — it combines small file sizes with broad compatibility.
AVIF offers the best compression available but comes with slower encoding times. HEIC works well within the Apple ecosystem but causes compatibility headaches elsewhere. SVG is unbeatable for logos, icons, and illustrations. TIFF is the professional standard for print and archival work.
The most common mistake people make is using the wrong format for their content type. Photos should never be PNG on the web. Logos should never be JPG. Screenshots should never use heavy lossy compression. Match the format to the content, and you will get the best balance of quality and file size every time.