Image Format Guide: JPG vs PNG vs WebP vs AVIF - Which to Use When

Two years ago, I designed a website with stunning product photos. I saved everything as PNG because "PNG is higher quality," right? The site looked amazing on my computer but took 15 seconds to load on mobile. Customers were bouncing before seeing a single product. When I finally learned the difference between image formats and converted everything to optimized JPEGs, load time dropped to 2 seconds and sales jumped 35%. The images looked identical to visitors, but file sizes were 80% smaller. That expensive mistake taught me: choosing the right image format isn't about quality alone—it's about balancing quality, file size, features, and browser support for your specific use case.

This guide explains every major image format—JPEG, PNG, WebP, AVIF, GIF, SVG—and when to use each one. You'll learn how each format compresses images differently, what quality vs file size trade-offs exist, which formats support transparency and animation, browser compatibility for newer formats, and practical decision frameworks so you always pick the right format. Whether you're building websites, creating social media graphics, or just trying to email photos without hitting attachment limits, understanding formats prevents wasted bandwidth and poor-quality images.

The Big Picture: Raster vs Vector

Before diving into specific formats, understand the fundamental difference between the two image types.

Raster Images (Pixel-Based)

Made of individual colored pixels arranged in a grid. Zoom in enough and you see squares. Formats: JPEG, PNG, WebP, AVIF, GIF.

Characteristics:

• Fixed resolution: 1920×1080 image has 2,073,600 pixels, no more, no less
• Loses quality when enlarged: Scaling up creates pixelation/blurriness
• File size increases with dimensions: 4000×3000 image is ~4x larger than 2000×1500
• Best for: Photographs, complex images with gradients and textures

Vector Images (Math-Based)

Defined by mathematical equations for shapes, lines, and curves. Format: SVG (plus AI, EPS for design work).

Characteristics:

• Resolution-independent: Scale infinitely without quality loss
• Small file sizes: A logo might be 2-10 KB regardless of display size
• Editable: Can change colors, shapes, text after creation
• Best for: Logos, icons, illustrations, charts, text-based graphics

JPEG: The Universal Standard

What is JPEG?

JPEG (Joint Photographic Experts Group) has been the web's dominant image format since the 1990s. It uses lossy compression—permanently discards data to achieve small file sizes.

How Compression Works:

JPEG analyzes image blocks (8×8 pixels), discards subtle color variations humans barely notice, and saves only essential information. Higher compression = more data discarded = smaller files but visible quality loss.

JPEG Strengths

• Excellent compression for photos: Can reduce file size 80-90% with minimal visible quality loss
• Universal browser support: Works everywhere—100% compatibility
• Small file sizes: Good for web performance and email attachments
• Adjustable quality: Choose compression level from 0-100%

JPEG Weaknesses

• No transparency: Can't have transparent backgrounds
• Lossy compression: Quality degrades each time you edit and re-save
• Poor for text/sharp edges: Creates artifacts (blocky distortions) around text and hard edges
• Not ideal for graphics: Logos and illustrations with flat colors look better in PNG

When to Use JPEG

• Photographs (portraits, landscapes, product photos)
• Images with gradients, shadows, complex textures
• Website hero images and backgrounds
• Social media photos
• Email attachments when file size matters

PNG: Lossless Quality with Transparency

What is PNG?

PNG (Portable Network Graphics) uses lossless compression—no data is permanently discarded. Every edit, save, and reload preserves perfect quality. Supports transparency via alpha channel.

Two Types:

• PNG-8: 256 colors maximum, smaller files, good for simple graphics
• PNG-24: 16.7 million colors, larger files, full photographic quality

PNG Strengths

• Lossless quality: No degradation from editing/re-saving
• Transparency support: Alpha channel for smooth transparency
• Sharp text and edges: Perfect for logos, text overlays, graphics
• Universal support: Works in all browsers and software

PNG Weaknesses

• Much larger than JPEG for photos: 3-5x bigger file sizes
• Not ideal for photographs: Unless you need transparency
• Slower to load: Large file size impacts page speed

When to Use PNG

• Logos (especially with transparency)
• Icons and UI elements
• Graphics with text overlays
• Images requiring transparent backgrounds
• Simple illustrations with flat colors
• Screenshots (text stays sharp)

WebP: Modern Efficiency

What is WebP?

Developed by Google in 2010, WebP provides superior compression compared to both JPEG and PNG. Supports both lossy (like JPEG) and lossless (like PNG) modes, plus transparency and animation.

WebP Strengths

• 25-35% smaller than JPEG: Same visual quality at significantly smaller size
• Better than PNG for graphics: Transparent PNGs become 20-50% smaller as WebP
• Versatile: One format handles photos, graphics, transparency, animation
• Good browser support: 97%+ (all modern browsers)

WebP Weaknesses

• Not universal: IE and very old Safari don't support it
• Requires fallback: Need JPEG/PNG backup for full compatibility
• Less software support: Some editing tools don't handle WebP well

When to Use WebP

• Modern website optimization (with JPEG/PNG fallback)
• Replacing both JPEG and PNG to simplify workflow
• When targeting users on modern browsers (most people in 2025)
• Situations where every KB matters (mobile apps, slow connections)

AVIF: Next-Generation Compression

What is AVIF?

AVIF (AV1 Image File Format) is the newest format, derived from video codec technology. Offers 30-50% better compression than WebP while maintaining higher quality.

AVIF Strengths

• Best compression available: 30-50% smaller than WebP, 50-70% smaller than JPEG
• Superior quality at low bitrates: Maintains detail better than other formats when heavily compressed
• Supports HDR and wide color gamut: Future-proof for high-quality displays
• Transparency and animation: Like WebP but better

AVIF Weaknesses

• Browser support still growing: ~90% as of 2025 (Safari added support in 2023)
• Slower encoding/decoding: CPU-intensive, especially on older devices
• Limited software support: Not all image editors support AVIF yet
• Requires multiple fallbacks: Need WebP + JPEG for full compatibility

When to Use AVIF

• High-traffic websites where bandwidth costs matter
• Hero images and large visuals
• When serving modern browsers (with WebP + JPEG fallback)
• Situations requiring maximum quality at minimum file size

GIF: The Animated Relic

What is GIF?

GIF (Graphics Interchange Format) from 1987 supports animation and transparency but limited to 256 colors. It's essentially obsolete for static images but survives due to ubiquitous animation support.

GIF Strengths

• Universal animation support: Every browser, every platform plays GIFs
• No playback controls needed: Loops automatically, no play button required
• Social media compatibility: Widely supported for memes and reactions

GIF Weaknesses

• Only 256 colors: Photos look terrible (banding, posterization)
• Huge file sizes for video: 5-second GIF can be 5-10 MB
• No sound: Silent animations only
• Better alternatives exist: WebP and AVIF support animation more efficiently

When to Use GIF

• Simple animations (loading spinners, 2-3 frame toggles)
• Social media memes and reactions (cultural norm)
• When you need broadest possible animation compatibility

Better alternative: Video formats (MP4, WebM) are 90% smaller than GIF for longer animations. Embed as `

SVG: Vector Graphics for the Web

What is SVG?

SVG (Scalable Vector Graphics) is XML-based vector format. Text file describing shapes, paths, and colors mathematically.

SVG Strengths

• Infinitely scalable: Looks perfect at any size—tiny icons to billboard-sized
• Tiny file sizes: Complex logos often 2-10 KB
• Editable with code: Change colors, animate elements with CSS/JavaScript
• Searchable and accessible: Text within SVG is readable by search engines

SVG Weaknesses

• Not for photographs: Can't represent complex images like photos
• Complexity increases file size: Very detailed illustrations become large
• Requires design software: Need Illustrator, Inkscape, or similar to create

When to Use SVG

• Company logos and brand marks
• Icons and UI elements
• Charts, graphs, diagrams
• Illustrations with solid colors and clean lines
• Any graphic that needs to scale (responsive design)

Format Decision Framework

When faced with an image, use this flowchart logic:

Practical Implementation Guide

Serving Modern Formats with Fallbacks

Use HTML `` element to serve modern formats with automatic fallbacks:

<picture>
  <source type="image/avif" srcset="photo.avif">
  <source type="image/webp" srcset="photo.webp">
  <img src="photo.jpg" alt="Description">
</picture>

Conversion Tools

Common Mistakes to Avoid

Mistake #1: Using PNG for Everything

"PNG is better quality" leads people to use it for all images. Result: 5x larger files that slow websites to a crawl.

Fix: Use PNG only for graphics with transparency or text. Photos should be JPEG or WebP.

Mistake #2: Saving JPEG at 100% Quality

JPEG 100% is massive with barely noticeable improvement over 85%. You're wasting bandwidth for imperceptible quality gain.

Fix: Use 75-85% quality for web. Only use 90%+ for print or professional photography.

Mistake #3: Ignoring Modern Formats

Sticking to JPEG/PNG in 2025 wastes 30-50% bandwidth. Modern formats exist for a reason.

Fix: Implement WebP (at minimum) with JPEG fallback. AVIF for high-traffic sites.

Mistake #4: Exporting Vector Graphics as Raster

Saving logos as PNG/JPEG creates unnecessarily large files that look blurry when scaled.

Fix: Keep logos as SVG. They'll be 10-20x smaller and scale perfectly.

Final Thoughts: Format Matters

Choosing the right image format isn't pedantic perfectionism—it's fundamental to web performance, user experience, and SEO rankings. A 5 MB PNG where a 500 KB JPEG would suffice isn't just wasteful; it's actively hurting your site's success.

The good news: format selection isn't complicated once you understand the basics. Photos = JPEG/WebP/AVIF. Graphics with transparency = PNG/WebP. Logos and icons = SVG. Follow these rules and you're ahead of most websites.

As of 2025, the optimal strategy for most websites is: SVG for vectors, AVIF with WebP + JPEG fallback for photos, PNG-8 for simple graphics if SVG isn't feasible. This combination delivers maximum performance while maintaining universal compatibility.