Text Diff Checker
Compare two pieces of text side-by-side and highlight every line and word change.
Quick answer: Text Diff Checker: compare two pieces of text side-by-side and highlight every line and word change. Runs entirely in your browser, free, no signup.
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A line-level diff shines when you need to answer "what changed between these two versions?" without opening a heavyweight editor. The comparison uses the same longest-common-subsequence approach as the Unix diff utility, so unchanged lines stay put while genuine insertions and deletions are highlighted in place — ideal for reviewing edited emails, contract clauses, config files, or generated output.
The ignore whitespace option is more important than it looks. Copy-pasted code and YAML frequently mix tabs with spaces or carry invisible trailing whitespace, which a naive diff flags as changes on every line. Turning that option on lets you focus on substantive edits instead of drowning in formatting noise.
For comparing two versions of a structured JSON document, a key-aware JSON diff understands that reordered keys are not really a change, which a plain text diff cannot. Use this tool for prose and free-form text; reach for the structured variant when whitespace and key order should be ignored by design.
Frequently asked questions
- How is this different from a Word 'Compare' feature?
- Word's compare needs both files to be Word documents and is heavy. This diff is instant, plain-text, and runs entirely in your browser — perfect for emails, code, JSON, prose or anything copy-pasteable.
- Does it ignore whitespace differences?
- Toggle 'ignore whitespace' to mask trailing spaces and tab/space mixes — useful when comparing source code or YAML.
- Will it scale to large files?
- Up to roughly a megabyte of text on each side runs in well under a second on a typical laptop. Beyond that, a desktop diff tool will feel snappier.
- Is my text uploaded?
- No — the diff runs entirely in your browser using a small JavaScript LCS implementation. Nothing leaves your device.
- Can I download the diff as a patch?
- Yes — copy the unified diff output to paste into a code review or apply with the <code>patch</code> CLI.