PNG vs WebP vs SVG: Which Image Format for Mobile App Assets?

Overview

Choosing the right image format is one of the most impactful decisions you can make for your mobile app's performance and visual quality. PNG, WebP, and SVG each solve different problems, and picking the wrong one leads to bloated APKs, blurry icons, or unnecessary rendering overhead.

This guide breaks down the technical characteristics of each format, compares them side by side, and gives you a clear decision framework for every type of asset in your project. If you are unfamiliar with how screen density affects image assets, read What is DPI? first.

PNG: The Reliable Raster Standard

PNG (Portable Network Graphics) uses lossless compression, meaning it preserves every pixel of the original image without any quality degradation. It supports full alpha transparency, making it the default choice for UI elements that need transparent backgrounds — app icons, overlay graphics, and toolbar images.

Because PNG is lossless, file sizes can be significantly larger than lossy alternatives. A typical 512 x 512 app icon in PNG might weigh 80-200 KB depending on complexity, while the same image in lossy WebP could be under 40 KB. For simple graphics with large flat-colour regions, PNG compresses efficiently. For photographs or images with subtle gradients, file sizes grow quickly.

PNG is universally supported across every version of Android and iOS with no compatibility concerns. It remains the required format for app store icons on both Google Play and the Apple App Store.

When PNG is the best choice

• App launcher icons (required by app stores)
• Raster icons with transparency that must work on all OS versions
• Screenshots and promotional graphics where lossless quality matters
• Photos that require an alpha channel (e.g., product cutouts overlaid on UI)

WebP: Smaller Files, Modern Support

WebP is a format developed by Google that supports both lossy and lossless compression modes, as well as alpha transparency in both modes. In lossy mode, WebP produces files that are typically 25-35% smaller than equivalent-quality JPEG files. In lossless mode, WebP files are roughly 26% smaller than PNG files according to Google's own benchmarks.

On Android, lossy WebP has been supported since API 14 (Android 4.0), and lossless WebP with alpha transparency since API 18 (Android 4.3). Given that the minimum API target for most modern apps is API 21 or higher, WebP is safe to use across virtually all active Android devices.

On iOS, WebP support arrived with iOS 14 (2020). If your app targets iOS 14 or later — which covers the vast majority of active iPhones — you can use WebP without any third-party libraries. For Flutter projects, Image.network() and Image.asset() both decode WebP natively on both platforms.

When to use WebP

• In-app photos and content images where file size matters
• Background images and splash screens
• Any raster asset where you can drop legacy OS support (below API 18 / iOS 14)
• Animated images as a replacement for GIF (WebP supports animation with better compression)

SVG: Resolution-Independent Vectors

SVG (Scalable Vector Graphics) is fundamentally different from PNG and WebP. Instead of storing a grid of pixels, SVG describes shapes, paths, and colours using XML markup. This means an SVG asset scales perfectly at any screen density without any loss of quality — you never need to generate mdpi, xhdpi, or xxxhdpi variants.

On Android, raw SVG files are not directly supported by the resource system. Instead, Android uses VectorDrawable, an XML format inspired by SVG. Android Studio can import SVG files and convert them to VectorDrawable automatically via the Vector Asset Studio. The resulting drawable/ic_*.xml files work on API 21+ natively, and on older versions via the AndroidX compatibility library.

In Flutter, the flutter_svg package renders SVG files directly at runtime. This avoids the conversion step and lets you ship a single SVG file that renders crisply on every device. iOS does not have native SVG rendering for image assets, but PDF-based vector assets in Xcode Asset Catalogs serve a similar purpose.

When to use SVG

• Monochrome or flat-colour icons and illustrations
• Logos that must render at many sizes without blurring
• UI elements like tab bar icons, navigation icons, and status indicators
• Any asset composed of geometric shapes rather than photographic content

Format Comparison

What About JPEG?

JPEG is a lossy format optimised for continuous-tone photographic images. It achieves excellent compression ratios for photos but does not support transparency. In mobile apps, JPEG is best suited for full-screen photo backgrounds, user-uploaded content, and any image that is purely photographic with no need for an alpha channel.

If you are shipping photo content and transparency is not required, JPEG often produces smaller files than PNG and comparable quality to lossy WebP. However, WebP at equivalent quality settings will still be 25-35% smaller, so JPEG is primarily useful when you need broad compatibility with older systems or server-side toolchains that do not yet support WebP.

Decision Framework: Which Format to Use

Use the following logic to determine the best format for each asset in your project:

1. Is the asset composed of geometric shapes, icons, or flat illustrations? Use SVG (or VectorDrawable on Android). You eliminate the need for multiple density variants entirely and keep file sizes minimal.
2. Is it a photograph or complex raster image without transparency? Use WebP in lossy mode for the best size-to-quality ratio. Fall back to JPEG only if your minimum OS target does not support WebP.
3. Is it a raster image that requires transparency? Use WebP lossless if your minimum targets are Android API 18+ and iOS 14+. Otherwise, use PNG.
4. Is it an app store icon or launcher icon? Use PNG. Both Google Play and the Apple App Store require PNG for store listing assets.
5. Is it an animated image? Use animated WebP over GIF. WebP animation offers better compression and colour depth than GIF's 256-colour palette.

For a deeper look at how density variants like drawable-mdpi through drawable-xxxhdpi work, see the Android drawable sizes guide.

Impact on App Size and Download Time

Image assets are one of the largest contributors to APK and IPA size. A typical app might include 50-200 image assets, each duplicated across 3-5 density buckets. If those assets use PNG exclusively, the total image payload can easily exceed 10-20 MB.

Switching from PNG to WebP for raster assets can reduce image payload by 25-35% with no visible quality loss. For a 15 MB image payload, that translates to roughly 4-5 MB saved — a meaningful reduction that improves download conversion rates, especially in markets with slower network connections.

Replacing raster icons with SVG-based VectorDrawables or flutter_svg assets eliminates the need for multiple density copies altogether. A single 2 KB SVG replaces five PNG files that might total 40-80 KB combined. Across dozens of icons, this adds up significantly.

For a comprehensive strategy on reducing your final binary size, read How to reduce app size with optimised images.

Best Practices

• Start with vector whenever possible. Icons, logos, and simple illustrations should be SVG or VectorDrawable by default. Only fall back to raster formats when the asset contains photographic detail or complex textures.
• Design at the highest density first. Create raster assets at xxxhdpi (4x) or @3x resolution, then scale down. Upscaling from a low-resolution source always produces blurry results.
• Use WebP as your default raster format. Unless you need to support Android below API 18 or iOS below 14, WebP gives you smaller files with equivalent or better quality than PNG and JPEG.
• Audit your asset pipeline regularly. As your app grows, outdated PNG assets accumulate. Periodically review and convert eligible PNGs to WebP or replace them with vectors.
• Automate density variant generation. Use App Image Kit to generate all required density variants from a single source image, avoiding manual resizing errors and saving time on every asset update.

Summary

There is no single "best" image format for mobile apps. PNG remains essential for app store icons and maximum compatibility. WebP should be your default for raster assets wherever platform support allows. SVG (via VectorDrawable or flutter_svg) is the optimal choice for icons and illustrations, eliminating density variants entirely.

The right approach is usually a mix: vectors for icons, WebP for photos and complex raster graphics, and PNG only where required. Combined with proper DPI-aware asset generation, this strategy keeps your app looking sharp on every device while minimising binary size and download time.