Frequently Asked Questions

Never. Every tool on ZeroUpload processes data exclusively in your browser using JavaScript Web APIs. No file, text, or data of any kind is transmitted to our servers or any third party. You can verify this by using your browser's network inspector — you'll see zero outbound data requests when using our tools.

No. We have no backend infrastructure that receives or stores user data. We don't even have a database of user sessions. The only data that persists is tool usage counts stored in your own browser's localStorage — this never leaves your device.

Yes — completely safe. The JSON formatter processes everything locally using JavaScript's native JSON.parse and JSON.stringify. Your API keys, tokens, and sensitive configuration never leave your browser tab.

We do not use tracking cookies, analytics that profile users, or any surveillance technology. We may use minimal technical cookies for functionality (such as remembering your theme preference), but these contain no personal information and are stored locally.

Yes, once the page is loaded, most tools work without an active internet connection since all processing is done in your browser. A connection is only needed to initially load the page and its scripts.

Passwords are generated using crypto.getRandomValues() — the browser's cryptographically secure random number generator. This is the same API used in security-critical applications. The character pool and length you select determine the entropy of each generated password.

Common causes: single quotes instead of double quotes, trailing commas after the last element, JavaScript-style comments (not valid in JSON), unescaped control characters in strings, or a missing closing bracket/brace. The error message shows the exact position of the issue.

If the original image is already highly optimized, re-compression may not reduce file size further. Our tool detects this and returns the original file with a warning rather than giving you a larger file. This is a feature, not a bug.

The image is drawn onto an HTML Canvas element and re-encoded as a new JPEG. This process creates a brand new image file that contains only the pixel data — all metadata layers (EXIF, XMP, IPTC) are discarded as they are not part of the Canvas rendering pipeline.

SHA-256 is the current industry standard for most uses. SHA-512 offers additional security margin. Avoid MD5 and SHA-1 for security-sensitive applications as they are considered cryptographically weak — use them only for non-security file integrity checks.

The diff checker uses a Longest Common Subsequence (LCS) algorithm to identify unchanged lines, then marks additions in green and deletions in red. It supports both a side-by-side split view and a unified view similar to 'git diff' output.

You can convert any browser-readable image (JPEG, PNG, WebP, BMP, GIF) to JPEG, PNG, or WebP output. You can also resize images during conversion by entering target dimensions. WebP is recommended for web use as it produces the smallest file sizes.

No — palette colors are saved in your browser's localStorage only. They persist between visits on the same device and browser but are never sent to any server. You can clear them at any time with the Clear button.

No — the optimizer removes invisible data like comments, metadata, and editor annotations that have no effect on rendering. Always use the before/after preview to verify the result before using the optimized file.

Yes — all tools are free forever with no hidden tiers, usage limits, or premium features. ZeroUpload is monetized through unobtrusive advertising, not paywalls.

No account is ever required. Open any tool and start using it immediately. We deliberately designed ZeroUpload to require zero friction — no sign-up, no email, no personal information.

Tools like the Image Compressor and EXIF Remover support multiple files in one session. The limit depends on your device's available memory rather than any artificial restriction we impose.

Absolutely — use our Contact page to send suggestions. We're actively building new tools and user feedback directly shapes our roadmap.