Palindrome Checker
Check if any word, phrase, or sentence is a palindrome instantly. Live results, character-by-character comparison, ignore case and punctuation. Free.
Palindrome Checker Tool
How to Use the Palindrome Checker
Type or paste your text
Enter a single word, phrase, or full sentence into the text box. The check runs instantly as you type.
Adjust the ignore options
By default the checker ignores letter case and punctuation, which is how most palindromes are scored. Toggle them off for strict matching.
Read the result
A green tick means it's a palindrome; a red cross means it isn't. The character-by-character comparison highlights matches and mismatches.
Try a famous example
Click the "Try an example" button to cycle through famous palindromes from literature and pop culture.
About the Palindrome Checker
A palindrome is any sequence of characters that reads identically forwards and backwards. The word itself comes from the Greek palin ("again") and dromos ("running") — literally "running back again." Simple word palindromes like level, radar, and kayak are the everyday cases; the more impressive sentence palindromes — "A man, a plan, a canal: Panama", "Madam, in Eden, I'm Adam", "Was it a car or a cat I saw" — only work once you strip out spaces, punctuation, and case. That stripping convention is what most palindrome checkers, including this one, follow by default. Toggle the strict-match options off if you need exact comparison instead.
Palindromes are deceptively rich. In mathematics, a palindromic number reads the same in both directions (1991, 2002, 12321); the famous 196 problem asks whether iteratively reverse-and-adding from 196 ever produces a palindrome (after billions of iterations, it still has not). In biology, a DNA palindrome is a sequence that reads identically when you reverse it and take the complement (A↔T, G↔C) — these palindromic restriction sites are where many restriction enzymes cut DNA, and they're foundational to genetic engineering. In computer science, the "longest palindromic substring" problem is a staple interview question and a classic application of dynamic programming.
"A man, a plan, a canal: Panama" — palindrome attributed to Leigh Mercer, 1948. Read it without spaces and you'll see: amanaplanacanalpanama. Reverse those letters and you get the same sequence back.
— a 75-year-old proof that English palindromes can be poetry
Palindromes across languages
English palindromes are constrained because English uses a 26-letter alphabet with frequency imbalances (E appears five times as often as W). Languages with more even letter distributions, like Finnish or Latin, produce palindromes more easily. The longest single-word palindromes in English are still relatively short — tattarrattat (12 letters, coined by James Joyce in Ulysses) is a widely cited candidate, while Finnish gives us saippuakivikauppias ("soapstone seller") at 19 letters. In Bahasa Malaysia and Bahasa Indonesia, palindromes work cleanly because the orthography is phonemic — phrases like kasur ini rusak ("this mattress is broken") demonstrate sentence palindromes that read naturally. Tamil, with its richer letter inventory, produces some of the longest sentence palindromes documented.
Why we check character-by-character
This tool runs in your browser, with no input sent anywhere. The character-by-character comparison view shows you exactly where a near-palindrome breaks — which letter pair mismatches. This is genuinely useful for puzzle constructors and crossword editors who need to verify their work, students learning about symmetry in language, and programmers practising for interviews. The check handles Unicode properly: Chinese, Japanese, Arabic, and Tamil text all work as long as the characters are well-formed. We do not normalise accented characters (é ≠ e by default) because in some languages they represent distinct phonemes; the strict-match toggle exposes this behaviour explicitly.
For longer texts (we cap at 10,000 characters), the check completes in well under a millisecond on modern hardware. There's no compilation, no virtual DOM, no library — just a tight loop comparing index i from the start with index length − 1 − i from the end. If you're curious, open DevTools and watch the timing. A 10,000-character palindrome check is genuinely cheap.
The Sator Square at Pompeii, and the 196 problem nobody has solved
The word itself is Greek. Palin ("again") + dromos ("running") = "running back again." Coined in English around 1638.
The Sator Square. A 2,000-year-old Latin palindrome — SATOR AREPO TENET OPERA ROTAS — found inscribed at Pompeii. It reads the same in four directions because it's a word square as well as a palindrome.
DNA palindromes matter. Restriction enzymes recognise palindromic sites in DNA to cut it precisely — the discovery recognised by the 1978 Nobel Prize in Physiology or Medicine.
The 196 problem is unsolved. Take 196, reverse it to 691, add → 887. Reverse 887 to 788, add → 1675. Keep going. After billions of iterations no palindrome has ever appeared. Whether one ever will is an open mathematical question.
"Was it a car or a cat I saw" remains one of the most-quoted English sentence palindromes — strip the spaces and it reads wasitacaroracatisaw both ways.
Joyce invented one. James Joyce coined tattarrattat in Ulysses (1922) — onomatopoeia for a knock on the door. At 12 letters it's one of the longest single-word palindromes in a major published novel.
02/02/2020 was rare, not unique. It was a palindrome in DD/MM/YYYY, MM/DD/YYYY and YYYY/MM/DD at once. The next date to manage all three is 12 December 2121, then 3 March 3030.
"Longest palindromic substring." The classic interview question can be solved in O(n) time using Manacher's algorithm (1975) — but most candidates only get to the O(n²) dynamic programming solution. Worth practising if you're job-hunting in tech.
Bahasa has palindromes too. Kasur ini rusak ("this mattress is broken") reads kasurinirusak in both directions.
This tool runs locally. Your text never leaves your browser. We don't log inputs, we don't analyse content, we don't even send analytics on what you type. Open DevTools and watch — only static assets load.
Frequently Asked Questions
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A palindrome is a sequence of characters that reads identically forwards and backwards. Single words like "level", "radar", "kayak", and "rotator" are simple palindromes. Sentence palindromes such as "A man, a plan, a canal: Panama" work once you strip out spaces, punctuation, and case differences — which is the standard convention this tool follows by default.
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By default no — they're ignored, which is the standard "literary palindrome" convention. Sentence palindromes like "Was it a car or a cat I saw" only work this way. Toggle "Ignore spaces & punctuation" off if you need strict exact-match checking instead, for example when verifying number palindromes or strict word puzzles.
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By default no. "Racecar" and "racecar" both count as palindromes. Toggle "Ignore case" off if you need strict case-sensitive matching — useful for code-related palindromes where letter case matters.
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10,000 characters, which handles essentially any palindrome you would encounter in practice. The check runs in your browser instantly even at maximum length — under one millisecond on modern hardware.
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No. Everything runs locally in your browser. No upload, no server-side processing, no analytics on what you type. You can verify this in DevTools: only the static asset bundle loads, nothing else. Safe for sensitive text and private notes.
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Yes. Chinese, Japanese, Tamil, Thai, Arabic, and other scripts all work as long as the characters are well-formed Unicode. The check compares characters by their code points. Bahasa Malaysia and Bahasa Indonesia work particularly well because their phonemic spelling produces clean palindromes.
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Yes, they work the same way. 12321, 1991, and 2002 are palindromes. Famous examples: 02/02/2020 was a palindrome date in DD/MM/YYYY, MM/DD/YYYY, and YYYY/MM/DD formats simultaneously. Mathematicians call any number that reads the same forwards and backwards a "numeric palindrome."
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In molecular biology, a DNA palindrome is a sequence that reads the same forwards on one strand as backwards on the complementary strand (A pairs with T, G pairs with C). These palindromic sites are where most restriction enzymes cut DNA, making them foundational to genetic engineering, PCR, and CRISPR. This tool doesn't implement biological complement matching — it does pure character comparison.
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No, by default we treat é, è, and e as different characters because in many languages they represent distinct phonemes (and thus different sounds in a palindrome). If you want unaccented matching, normalise your text before pasting it in — most text editors offer a "remove diacritics" command.
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Yes — palindrome detection is in the public domain, the algorithm is trivial, and any output from this tool is yours to use however you like. We just supply the check; the words, phrases, and verified palindromes you discover belong to you.
Method & sources
How it computes
Optionally folds case and drops everything that is not a letter or digit in any script (accents are kept distinct), then compares code point i with its mirror and shows where a near-palindrome breaks. Up to 10,000 characters, in the browser.
What this tool implements
- Until this review the punctuation filter was [^a-z0-9], which deleted every non-ASCII letter: 上海自来水来自海上 and été both failed as "fewer than 2 characters". The filter now keeps letters and digits of every script, and comparison is by code point.
- Manacher (1975) finds palindromic structure in linear time; this tool needs only the simpler two-pointer check for a yes/no answer.
- 02/02/2020 was a palindrome in DD/MM/YYYY, MM/DD/YYYY and YYYY/MM/DD at once; the next such date is 12 December 2121 (checked by enumerating every date).
Sources
- Manacher G. A New Linear-Time "On-Line" Algorithm for Finding the Smallest Initial Palindrome of a String. J ACM. 1975;22(3):346-351. https://doi.org/10.1145/321892.321896
- The Nobel Prize in Physiology or Medicine 1978 — Arber, Nathans and Smith, for the discovery of restriction enzymes. https://www.nobelprize.org/prizes/medicine/1978/summary/
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