Frequently asked questions.

No. All compression happens entirely within your web browser using modern web APIs. Your files never leave your device, ensuring 100% privacy. ZeroPNG does not have any server-side image processing infrastructure, everything runs locally on your computer.

No. ZeroPNG can only access the files you explicitly select or drag-and-drop into the application. It runs in a sandboxed browser environment and has no access to your file system beyond what you choose to share.

The only data ZeroPNG stores locally is your theme preference (dark/light mode) in your browser's localStorage. No images, file names, or usage data are ever stored. You can clear this at any time through your browser settings.

Simply drag and drop your images onto the drop zone, or click it to browse for files. Adjust the quality slider and output format if needed, then hit "Compress All." You can download files individually or as a ZIP archive.

Input formats: PNG, JPEG, WebP, AVIF, and GIF.
Output formats: PNG, JPEG, WebP, and AVIF. You can also keep the original format while still reducing file size.

For web viewing, WebP or AVIF offer the best compression. If you need maximum compatibility, stick with JPEG (for photos) or PNG (for graphics with transparency). Use "Keep Original" to reduce size without changing the format.

The quality slider (10–100%) controls how aggressively the image is compressed. Higher values retain more detail but produce larger files. For most images, 70–80% offers an excellent balance between quality and file size with virtually no visible difference.

Yes! Use the "Max Width" dropdown to cap the output width. Options include 4K (3840px), 1920px, 1280px, 800px, and 400px. The aspect ratio is always preserved. Select "No Resize" to keep the original dimensions.

There is no hard limit. ZeroPNG uses your computer's processing power, so you can compress hundreds of images at once. Processing speed depends on your device's capabilities and the size of the images.

Yes! Simply copy an image (e.g., a screenshot) and paste it directly onto the page using Ctrl+V / Cmd+V. ZeroPNG will add it to the queue automatically.

Because the server doesn't process the images (your computer does all the work!), our hosting costs are essentially zero. There are no artificial limits, no premium tiers, and no hidden fees.

Yes! Once you load the site for the first time, it installs a Service Worker that caches the entire app. You can disconnect from the internet and continue compressing images. Everything works the same as online.

We recommend keeping individual files under 20 MB to ensure smooth processing without crashing your browser tab. However, there are no hard server limits since everything is processed locally on your device.

ZeroPNG uses color quantization to reduce the number of colors in a PNG image (similar to TinyPNG). A 24-bit PNG with millions of colors is reduced to an 8-bit palette of 256 colors or fewer, achieving 60–80% reduction while maintaining visual quality.

No, your original files are never altered. ZeroPNG creates new, optimized versions of your images that you can download individually or together as a single ZIP file. Your originals remain completely untouched.

ZeroPNG works on all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience and full format support (especially AVIF), we recommend using the latest version of Chrome or Edge.

AVIF uses the AV1 codec which is computationally intensive. The browser's built-in Canvas API handles AVIF encoding, and it requires significantly more processing time than JPEG or WebP. The trade-off is that AVIF produces the smallest files of any format.

Use ZeroPNG's free Image Converter to convert between PNG, JPG, WebP, and AVIF formats. Simply drop your images, choose your target format from the dropdown, adjust quality if needed, and click "Convert All." All conversion happens in your browser, no uploads required.

WebP is the best format for converting PNG images for web use. WebP produces files 25–35% smaller than PNG while supporting transparency. It's supported by 97%+ of browsers in 2026. For maximum compression, try AVIF which offers even smaller files (~50% smaller than JPEG) but has slightly less browser support (~92%).

Yes, when you convert JPG to PNG using ZeroPNG's converter, the output is lossless PNG. However, note that since JPG is already a lossy format, converting to PNG won't recover quality lost during the original JPEG compression. The PNG output will be a lossless copy of the JPEG data, typically in a larger file size.

WebP offers good compression with 97%+ browser support, it's the safest modern format choice. AVIF offers even better compression (up to 50% smaller than JPEG) but has slower encoding, slightly less browser support (~92%), and can struggle with very detailed textures. For most users, WebP is the recommended choice; use AVIF when maximum compression matters most.

Absolutely. Drop or select as many images as you need, there's no limit. All files are converted simultaneously using your browser's processing power. Download them individually or grab everything as a single ZIP file.

Yes, when converting to formats that support transparency, PNG, WebP, and AVIF all preserve alpha channels. If you convert to JPEG, transparent areas will be filled with a white background since JPEG doesn't support transparency.

Use ZeroPNG's free HEIC to JPG Converter. Simply drag and drop your iPhone HEIC photos, they auto-convert to high-quality JPG instantly. No signup, no watermarks, no file limits. All conversion happens in your browser so your photos are never uploaded to any server.

HEIC (High Efficiency Image Container) is Apple's default photo format on iPhone and iPad since iOS 11. It uses the HEVC codec to store photos ~50% smaller than JPEG. Most Windows PCs, Android devices, Chrome, Firefox, and many websites can't open HEIC files natively, that's why a HEIC to JPG converter is essential.

For iPhone photos, JPG is recommended - it produces much smaller files with excellent quality, ideal for sharing via email, social media, and web. Choose PNG only if you need perfect lossless quality. HEIC to JPG at 92% quality is the sweet spot for most users.

Yes, ZeroPNG's HEIC converter is the most private option available. Unlike other online converters that upload your photos to remote servers, ZeroPNG processes everything 100% in your browser using client-side JavaScript. Your iPhone photos never leave your device.

Windows doesn't natively support HEIC files. You can either install the HEIF Image Extensions from the Microsoft Store (may require a paid HEVC codec), or use ZeroPNG's free online HEIC to JPG converter to instantly convert your HEIC files to universally compatible JPG format.

On your iPhone, go to Settings → Camera → Formats and select "Most Compatible" instead of "High Efficiency." This makes your iPhone save new photos as JPEG. For existing HEIC photos on your camera roll, use ZeroPNG's HEIC converter to batch convert them to JPG.

Use ZeroPNG's free Image Cropper tool. Simply upload your image, adjust the selection box to your desired area, and click "Crop Image." You can then download the perfectly cropped version instantly. Everything happens 100% in your browser for total privacy.

ZeroPNG includes built-in presets for popular platforms: Square (1:1) for Instagram posts, Portrait (4:5) for feed photos, Stories/Reels (9:16) for vertical content, and Landscape (16:9) for YouTube or Facebook covers.

Yes! You can manually enter specific Width and Height in pixels, or choose "Custom" from the aspect ratio menu to free-form drag the crop box to any size. The dimensions update in real-time as you resize.

No. ZeroPNG's Image Cropper uses the high-resolution source data to create your crop. Unless you also choose to resize the output to a smaller resolution, your cropped image will maintain the same pixel quality as the original photo.

Selecting any preset (like 1:1 or 16:9) automatically locks the aspect ratio. This ensures that no matter how you resize the crop box, it maintains the correct proportions. Choose "Custom" if you want to unlock it and resize freely.

Simply drop your image into ZeroPNG's Image Watermark tool, enter your text or upload a logo, adjust the position, size, and opacity, then click "Apply & Download." No sign-up, no uploads, everything runs in your browser.

Yes! Change the watermark type to "Logo (Image)" and upload your specific PNG or SVG logo. You can then scale and position it exactly where you want on the base image.

No. ZeroPNG's watermarking tool processes your images at their original quality. You can also choose your preferred output format (JPEG, PNG, or WebP) when downloading.

Currently, the watermarking tool processes one image at a time to ensure precise placement and preview. However, since it runs entirely in your browser, there's no limit to how many images you can process sequentially.