Unicode Text Compare

Compare Unicode strings online

This tool compares two original strings exactly, then separately compares their NFC, NFD, NFKC and NFKD normalization forms, their Unicode code-point sequences, their grapheme-cluster sequences, and a lowercase-transformed comparison. It detects invisible-character differences, reports the first difference, and shows line, whitespace and byte metrics. Both inputs are preserved exactly and everything runs locally in the browser.

Unicode normalization comparison example

Text A contains the precomposed character U+00E9. Text B contains U+0065 followed by U+0301 COMBINING ACUTE ACCENT.

Text A: café
Text B: café

Exact match: No. Grapheme sequence match: Yes. Code-point sequence match: No. NFC match: Yes. NFD match: Yes. Text A code points: 4. Text B code points: 5. Text A UTF-8 bytes: 5. Text B UTF-8 bytes: 6.

Exact match vs visual match

Strings can render identically while containing different code points. Exact equality compares the stored UTF-16 sequence exactly as written. Grapheme comparison compares user-perceived character segments and treats canonically equivalent forms as matching. Visual similarity is not guaranteed by either result: fonts and rendering engines can affect appearance, so security-sensitive decisions should not rely on how text looks alone.

NFC, NFD, NFKC and NFKD

NFC and NFD are canonical normalization forms and preserve meaning: NFC composes characters where possible, and NFD decomposes them into a base character plus combining marks. NFKC and NFKD additionally apply compatibility mappings, which can merge distinctions such as fullwidth forms, ligatures, circled characters, superscripts and other presentation forms. A match after any of these forms does not mean the original inputs were identical, and this page always reports whether each input actually changes under each form.

Code points and grapheme clusters

A code point is one Unicode value. A grapheme cluster is a user-perceived character and can contain multiple code points, as combining marks and emoji sequences demonstrate. This tool can show a diff at either level: a code-point diff finds the first Unicode value that differs, while a grapheme diff finds the first user-perceived character that differs, even when it spans several code points. See What Is a Grapheme Cluster? and Code Points vs Code Units.

Case-insensitive and casefold comparison

This tool currently offers a lowercase comparison using JavaScript's lowercase mapping, applied both on its own and combined with NFC and NFKC normalization. This is not the same as full Unicode case folding, which is a locale-independent mapping designed specifically for caseless matching and can behave differently from simple lowercasing for some letters. The lowercase comparison here is clearly labeled as lowercase, not casefold.

Invisible-character differences

Zero-width spaces, joiners, bidirectional controls, special spaces, soft hyphens, variation selectors and control characters are real code points that affect exact and code-point comparisons even though they have little or no visible width. Unicode normalization does not remove most of these characters. Some are meaningful and should not be assumed unwanted. Use the Invisible Character Detector for a detailed, per-character inspection of either string.

First difference and detailed diff

The first difference is reported at the grapheme level, showing the constituent code points on each side. Detailed diffs show insertions, deletions and replacements at the grapheme, code-point and line level, using a proper sequence-diff algorithm rather than lining up positions one by one, so a single insertion does not appear to change every following row. Hidden characters are always shown with a visible, bracketed code-point label.

How to use the comparer

1. Paste the first string into Text A.
2. Paste the second string into Text B.
3. Run the comparison or review live results.
4. Check exact, normalization, grapheme and case results.
5. Inspect the first difference and detailed diff.
6. Copy or download the comparison report.

Common use cases

• Debug strings that look identical but compare differently.
• Compare precomposed and decomposed Unicode text.
• Find zero-width or non-breaking-space differences.
• Inspect database and API comparison failures.
• Compare normalized identifiers.
• Review case-insensitive matching behavior.
• Debug line-ending and whitespace differences.
• Create Unicode comparison test fixtures.

Privacy and local processing

Comparison runs with JavaScript directly in your browser. Your text is not submitted to UnicodeNow servers.

Frequently asked questions