Frequently Asked Questions (Index)
Are my images uploaded to any remote server or cloud service?
No. Absolutely zero bytes of your image data are ever uploaded to any remote server or third-party service. SnapWap executes all image decoding, resizing, color quantization, and re-encoding 100% inside your device's web browser using native-speed WebAssembly (WASM) and Web Workers. Your files never leave your local machine.
Is SnapWap safe for confidential documents, personal photos, and sensitive data?
Yes. Because processing is entirely client-side, SnapWap operates under strict zero-knowledge security. Whether you are optimizing confidential business contracts, financial scans, medical records, or private personal photographs, neither SnapWap nor any third-party infrastructure has access to your images. You can even disconnect your internet connection after the page loads and continue compressing files offline.
Can I use SnapWap offline without an active internet connection?
Yes. Once the web application and its WebAssembly codec binaries are cached by your browser, all core compression features work completely offline. Network connectivity is only used to initially load the static website assets; no backend API calls or remote workers are required to process images.
Does SnapWap track or log my image dimensions, file names, or metadata?
No. SnapWap collects zero image analytics, telemetry, or metadata tracking. Any metadata stripping (such as EXIF, GPS location coordinates, and camera serial numbers) is done intentionally on your device during preprocessing to protect your personal privacy and reduce output file size.
Which format should I choose: AVIF, WebP, or MozJPEG?
The best format depends on your target audience and use case:
• AVIF (AV1 Image File): Offers the highest compression efficiency available today (often 20-50% smaller than WebP at comparable visual quality). Excellent for photography and modern web applications (supported by Chrome, Safari 16+, Firefox).
• WebP: The universal modern web format. Provides universal browser support (97%+ of global browsers) and excellent compression for both lossy photos and lossless graphics with transparency.
• MozJPEG: The gold standard for universal backwards compatibility. Choose MozJPEG if you need files that display on legacy devices, email clients, social platforms, or desktop printers while achieving smaller byte sizes than standard JPEG encoders.
Why does JPEG XL (JXL) show an "in-browser preview unavailable" warning in Chrome and Firefox?
SnapWap successfully encodes fully standard-compliant .jxl files using libjxl WebAssembly. However, while Safari 17+ and iOS 17 natively display JPEG XL images, Chrome and Firefox have not yet enabled default JPEG XL rendering in their stable browser engines. When you encode to JXL in SnapWap, you can safely download the resulting file and inspect byte statistics, but the live visual canvas falls back to an informational notice on browsers that lack native JXL decoders.
What is the difference between lossy and lossless compression in SnapWap?
Lossless compression (available in WebP Lossless, PNG, and JPEG XL Lossless) reduces file size by removing redundant data encoding without modifying a single pixel value. The decoded image is mathematically identical to the original. Lossy compression (MozJPEG, WebP Lossy, AVIF) selectively discards subtle visual nuances that the human eye cannot perceive, achieving dramatically higher compression ratios (often 70-90% byte reductions).
What is Color Quantization and how does libimagequant reduce PNG size?
Color Quantization is the mathematical process of converting a 24-bit or 32-bit Truecolor image (containing millions of distinct colors) into an indexed 8-bit palette (2 to 256 colors). SnapWap integrates libimagequant compiled to WebAssembly. By smartly selecting the optimal color palette and applying Floyd-Steinberg error-diffusion dithering, it reduces PNG file sizes by up to 60-80% with virtually imperceptible degradation.
How does the Target File Size search algorithm work?
Instead of forcing users to guess quality numbers repeatedly, SnapWap includes an automated 2-phase logarithmic search. Enter your target budget (e.g. "150 KB"), and the algorithm iteratively encodes the asset at varying quality thresholds, converging to the maximum visual fidelity that fits under your exact byte budget in milliseconds.
Which resampling filter should I use when resizing images (Lanczos3 vs Mitchell vs Catmull-Rom)?
• Lanczos3: Best for sharp photographic downscaling and preserving high-frequency textural details.
• Mitchell-Netravali: Balanced filter providing a smooth compromise between sharpness and ringing artifacts.
• Catmull-Rom: High-sharpness cubic spline filter, ideal when downsampling moderately soft images.
• HQx / Nearest Neighbor: Perfect for pixel art, retro graphics, and crisp UI screenshots without blurring edges.
How does the Side A vs. Side B comparison slider and difference heatmap work?
SnapWap's TwoUp comparison canvas renders the original source (Side A) and optimized output (Side B) with synchronized 1:1 pan and exponential zoom running at 120 FPS via GPU transform acceleration. The difference heatmap mode computes perceptual pixel deltas ($|R_1 - R_2| + |G_1 - G_2| + |B_1 - B_2|$) in real-time, highlighting exactly where compression artifacts or color shifts occur.
Can I compress multiple images simultaneously and download them together?
Yes. SnapWap supports multi-file batch processing. You can drag and drop dozens of images into the batch drawer, configure unified compression settings across all files or tune them individually, and download the entire collection in a single structured ZIP archive generated client-side via JSZip.
Is there a limit on image resolution or file size?
SnapWap has no artificial paywalls or server upload limits. Because operations occur inside your browser, the only constraint is your device's available RAM and the browser's WebAssembly memory allocation cap (typically 2 GB to 4 GB in modern 64-bit browsers). Images up to 30-40 megapixels compress comfortably on modern laptops and desktop computers.
How is SnapWap different from Google Squoosh or TinyPNG?
Compared to TinyPNG, SnapWap is 100% private (zero cloud uploads, zero wait queues, no file size limits). Compared to Google's original Squoosh.app (which is an unmaintained project), SnapWap features a complete multi-file batch queue, an automated target size optimizer, multithreaded SIMD codec acceleration, an interactive visual difference heatmap, and a modern Next.js 16 + React 19 architecture.
Is SnapWap free for commercial use?
Yes. SnapWap is free software licensed under GPL-3.0-or-later. You can use it freely for personal, commercial, and professional web development projects without fees or account registration.