Check if text is a palindrome
Configurable normalization — case-insensitive and ignore non-alpha by default. Live result + visual comparison.
How to check palindromes
Normalizes the input (lowercase, strip punctuation by default), then compares it to its reverse.
- 01
Type or paste
Words, phrases, even numbers.
Tokenisation is Unicode-aware via
\p{L}\p{N}property classes — so accented letters, ideographs, and emoji code points all count correctly.textUTF-8Unicodecode pointsliveinput · textraw · UTF-8A man a plan a canal Panama
loaded · UTF-8UTF-8 · ready - 02
Normalize
By default: lowercase, strip non-letter/digit chars.
Live re-counts run on every keystroke through a memoised reducer, so even multi-megabyte inputs stay smooth in the editor.
normalizelivememoisedoptionssnappynorm · optionslower+strip · liveamanaplanacanalpanama
options applied · livelive - 03
Reverse + compare
Reversed string should match the normalized one.
Output preserves the original line endings (
\nvs\r\n) and trailing whitespace is reported separately so you can spot diff-only changes.compareline endingswhitespacediff-cleanreproducibletest · countedequal · readynorm === reversed
counted · livecounted - 04
Verdict
✓ palindrome or ✗ not — with the comparison shown.
Copy writes via the Async Clipboard API; downloads ship as
text/plain; charset=utf-8— nothing leaves your tab.resultclipboardtext/plainblobclient-side✓ · copiedready · done✓ palindrome
shipped · ready to shipsuccess
Text-processing fundamentals worth knowing
Tokenise with Unicode classes
Use \p{L}\p{N} with the u flag so accents, ideographs, and emoji count properly.
Normalise line endings
Convert \r\n to \n before diffing or hashing — Windows-vs-Unix endings produce phantom changes.
Mind invisible characters
Zero-width joiners, BOMs, and non-breaking spaces look identical to ASCII space. Strip them before comparison or storage.
Stream don’t slurp
For multi-megabyte text, iterate line-by-line rather than loading everything to memory — keeps the tab responsive.
Choose collation deliberately
Default JS sort is code-point order, not human alphabetical. Use Intl.Collator for locale-aware sorting.
Re-run after normalisation
NFC vs NFD changes byte length but not visible glyphs. String.prototype.normalize() before counts and comparisons.
When to check palindromes
Puzzles, games, fun.
Word puzzles
Quick verification for crossword clues. Tokenisation uses Unicode property classes (\p{L}, \p{N}) with the u flag so accents, ideographs, and emoji code points all count correctly. Surrogate-pair-aware counts mean 🚀 weighs 1, not 2.
Unicode-correctNumeric palindromes
12321, 1001 — non-alpha mode still works. Result updates as you type — paste and watch totals settle in milliseconds even on multi-megabyte inputs. Heavy work runs through a memoised reducer so the editor never janks.
diff-cleanEducational demo
Demonstrate string algorithms. Output normalises line endings to LF for clean diffs across platforms. Windows-vs-Unix CRLF mismatches disappear, which keeps git blame honest and review comments focused on real changes.
instant countsCoding interviews
Test edge cases quickly. Code-point counts are stable across NFC/NFD normalisation. Pair with the Reading Time Calculator to layer scan-time on top of raw counts, useful for editorial budgets and SEO meta-description limits.
platform-awareName fun
Find palindromic names: Ava, Hannah, Bob. All processing runs client-side — paste sensitive or pre-publish copy without it leaving the tab. The clipboard API writes UTF-8 text/plain so it survives transit to any editor or CMS.
code-point-accurateDNA sequences
Some biology homework involves palindromic DNA. Same input plus same options always produces identical output, so the tool is safe to embed in CI scripts or doc-generation pipelines without race conditions.
losslessFrequently asked questions
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