Frequently asked questions
Everything people usually ask about ImageZap. If you can't find your answer, write to us from the contact page.
Privacy and how it works
Are my images uploaded to a server?
No. ImageZap uses codecs compiled to WebAssembly that run in your browser. Files never leave your device; you can verify it by opening the Network tab in developer tools while you convert.
Where are the images I add stored?
In your browser's local storage (IndexedDB), so you can switch format or quality without uploading them again, even after reloading the page. They're removed when you press Clear, remove an image or clear the site data.
Is EXIF metadata removed?
Yes. When re-encoding, only the pixels are kept: EXIF data, including GPS location and camera model, is not copied. Orientation is applied before converting so the photo is displayed the right way up.
Limits
How many images can I convert?
As many as you like. There's no per-batch limit and no daily quota. For very large batches, consider turning off Convert automatically so you can tune settings first and convert afterwards.
Why is there a 30 MB per-file maximum?
An image is decompressed in memory at 4 bytes per pixel: a 50-megapixel photo takes around 200 MB before encoding. The limit keeps the browser, especially on phones, from running out of memory.
Which input formats are supported?
JPG, PNG, WebP, AVIF, JPEG XL, GIF (first frame) and BMP. HEIC/HEIF works in browsers that can decode it, such as Safari.
Formats and quality
Which format should I use?
For photos on the web, AVIF with WebP or JPEG as a fallback. For screenshots with text or graphics with transparency, lossless WebP or PNG. If in doubt, generate several formats at once and compare file sizes.
Why is the PNG output bigger than my JPEG?
PNG is lossless: it stores every pixel exactly, and for photos that takes much more space than a JPEG. Only use PNG when you need exact pixels or lossless transparency.
What quality should I choose?
Start with the Balanced profile (AVIF 60, WebP 80, JPEG 82). If you see artifacts in gradients or edges, raise it by 5–10 points or use High quality. For thumbnails you can go lower without anyone noticing.
What is 4:4:4 chroma subsampling?
Most codecs halve color resolution (4:2:0) because the eye is less sensitive to color than to brightness. On screenshots, logos or text over colored backgrounds this causes blurry edges; 4:4:4 keeps color at full resolution.
Why can't I see the JPEG XL preview in my browser?
Today only Safari displays JPEG XL natively. ImageZap produces the file correctly and decodes it with WebAssembly for the comparer. If you publish it on a website, serve it inside <picture> alongside AVIF or WebP.
Using the tool
Can I switch formats without uploading the images again?
Yes. Change the format or any setting and the images are regenerated. If you turn off automatic conversion, an Apply changes button appears.
Can I use different settings for one image?
Yes. Open that image in the comparer and move the quality control: the change only affects that image. The Use global settings button removes the customization.
What are responsive variants?
Versions of the same image at several widths (for example 640, 1280 and 1920 px) to use with srcset. The browser downloads the best one for each screen. The code generator writes srcset and sizes for you.
Are there keyboard shortcuts?
Yes: Ctrl/Cmd + V pastes images from the clipboard, Ctrl/Cmd + Enter converts and Ctrl/Cmd + S downloads the ZIP.
Is ImageZap free?
Yes, with no sign-up and no watermarks. The site is funded by a small number of ads on content pages.