About Diff Checker
Paste an original and a changed version of any code, config, or prose to see added and removed lines highlighted side by side with line numbers. Toggle whitespace-insensitive comparison for reformatted code. Everything happens locally in your browser: nothing is uploaded, stored, or logged. This focused Diff Checker page is designed for developers, writers, and reviewers checking exactly what changed between two versions of code, config, contracts, or copy. It opens directly to the working tool, rather than hiding the function inside a general converter or account dashboard.
The source is evaluated by a purpose-built parser or browser API in the current tab; it is not submitted to a remote formatter, compiler, or logging service. Your filename and file contents stay on the device. There is no upload queue, temporary cloud copy, account record, or server-side conversion job to delete later. That makes the tool practical for personal records, work material, and drafts that should not be handed to an unknown processing service.
The important limitation is straightforward: Comparison is line by line and works best up to about 2,000 lines per side; changes inside a line show as one removed and one added line. Knowing that boundary helps you choose the right source file and check the result before relying on it. Processing speed and maximum size depend on your browser and available device memory, which is the honest trade-off for doing the work locally.
FileForge charges nothing for this tool and does not add a watermark. Once the page and its processing engine have loaded, the operation can continue without sending the file over the network. Use the numbered steps below, download the result, and review it before replacing an original file.