Batch File Change Detector

A batch file change detector is a tool that compares two sets of files - a Before set and an After set - to identify exactly which files were added, removed, modified, or left unchanged. It is useful for deployment verification, security auditing, backup integrity checks, data migration validation, and any scenario where you need to track file-level changes across a group of files.

The tool compares files with the same name in both sets. First, it checks if the file sizes differ - a different size almost always means the content changed. For files with the same size, you can enable SHA-256 content hashing for definitive verification. The tool computes the hash of each file and compares them; different hashes mean different content. This catches modifications that preserve the exact file size.

SHA-256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function that produces a unique 64-character fingerprint for any given data. Even the smallest change to a file - a single byte flipped, a space added, or a character changed - produces a completely different hash. The tool uses the browser's built-in Web Crypto API to compute SHA-256 hashes, ensuring fast and accurate file comparison without any network calls.

There is no hard limit on the number of files you can upload. The tool processes everything locally in your browser, so the practical limit depends on your device's memory and processing power. For very large batches (hundreds or thousands of files), the hashing step may take longer. You can disable content hashing for faster comparison when size-only checking is sufficient.

The tool compares files by their full filenames (including any path components). When you drag and drop files from different folders, the browser typically provides just the file name without the full directory path. Files with the same name are considered the same file for comparison purposes. For more precise comparison with directory paths, consider grouping files into separate Before and After folders before uploading.

Absolutely. All processing is done entirely within your browser using JavaScript. Your files are never uploaded to any server - the tool reads the file names, sizes, and optionally computes content hashes using the browser's Web Crypto API. No file content is transmitted, stored, or logged. When you close or refresh the page, all data is discarded. This makes the tool safe for comparing sensitive files.

Common use cases include: verifying deployment packages before and after release, auditing for unauthorized file changes after a security incident, validating data migrations between storage systems, comparing software version builds for QA, checking backup integrity against originals, tracking project file changes during restructuring, and analyzing digital forensic evidence snapshots.

Currently, the tool matches files by filename to determine which files correspond between the Before and After sets. This is the most common and practical approach for batch file comparison. If you need to compare files with different names, you can rename them to match before uploading, or use the tool for individual file comparison where you can match files manually.

Yes, the Batch File Change Detector works with any file type - documents, images, audio, video, archives, executables, source code, text files, and binary files. The tool does not read or interpret file content; it only compares filenames, sizes, and optional cryptographic hashes, which work universally across all file formats.

Added files (green) are new files that appear in the After set but were not present in the Before set. Removed files (red) were present in the Before set but are missing from the After set. Modified files (amber) exist in both sets but have different content (different size or hash). Unchanged files (gray) are identical in both sets. The summary shows total counts and sizes for each category.