2026-09-09
Diffchecker is the name most people already know for comparing two blocks of text, and it does the job well. The reason to look for an alternative is usually specific: at least one of the two things you're comparing is a config file, an env snippet, or a chunk of code with a real secret or credential sitting in it, and pasting both versions into a tool that sends them to a server for comparison isn't something you want to do for that particular diff.
Diffchecker computes its diff server-side — both inputs are sent to compare them, same as most web-based diff tools. For a public snippet or a harmless config, that's a non-issue. For something with an API key, a database URL with credentials in it, or genuinely private text, it's worth avoiding on principle even if nothing bad would actually happen.
Code Diff Viewer does a line-by-line comparison of two blocks of text or code, highlighting additions and deletions, computed entirely client-side — nothing you paste into either panel is transmitted anywhere. It's a line-level diff, matching how most code review tools show changes, not a fine-grained word-by-word comparison within a line.
Diffchecker supports comparing images and PDFs in addition to plain text, which is genuinely broader coverage than a text-focused diff tool offers. If you need to diff two images pixel-by-pixel or compare rendered PDF pages rather than extracted text, that's outside what a code-focused diff viewer is built for.
For comparing code, config, or any text you'd rather keep off a server, Code Diff Viewer does the comparison locally with no meaningful loss of functionality for the plain-text case. For image or PDF-level comparison, Diffchecker's wider format support is the more complete tool.