Palindrome Checker
Type a word, a number or a whole sentence and see at once whether it reads the same backwards, with spaces, punctuation, capitals and accents ignored as you choose. If it does not, the checker shows where the two ends first disagree. Paste a longer text to find every palindromic word and sentence in it. Runs in your browser. Free, no sign-up.
One per line to check several at once. Spaces, punctuation and capitals are ignored unless you change the options.
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Type or paste something to check.
Runs entirely in your browser — nothing is uploaded.
How to Use the Palindrome Checker
- Pick a mode. Check a phrase tests what you type; Find palindromes in a text searches a longer passage.
- Enter your text. One item per line checks several at once and gives a line-by-line table.
- Set the options. By default capitals, spaces, punctuation and accents are ignored, which is how people judge sentence palindromes. Untick any of them to be stricter.
- Choose letters or words. Comparing by letters is the usual test. Comparing by whole words checks sentences that read the same word by word.
What Counts as a Palindrome
A palindrome reads the same forwards and backwards. The word comes from the Greek for "running back again". Single words (kayak, level, rotator, deified), numbers (12321), and sentences all qualify. Sentences are judged by their letters alone: "A man, a plan, a canal: Panama" is a palindrome because amanaplanacanalpanama is. The checker follows that convention by default.
A second kind works word by word rather than letter by letter. "Fall leaves after leaves fall" reverses to itself as a list of words, though not as a string of letters. Switch to Whole words to test for it.
How the Options Change the Answer
| Text | Default | Capitals matter | Spaces and punctuation count | Accents matter |
|---|---|---|---|---|
| Madam | Yes | No | Yes | Yes |
| A man, a plan, a canal: Panama | Yes | No | No | Yes |
| Never odd or even | Yes | No | No | Yes |
| Ésope reste ici et se repose | Yes | No | No | No |
Each column changes one setting from the default, in which capitals, spaces, punctuation and accents are all ignored.
Spaces and punctuation are the setting that matters most. With them counted, only text whose spacing is itself symmetrical passes — a b a does, never odd or even does not. Accents matter for languages such as French: the sentence "Ésope reste ici et se repose" is a palindrome only when É and e are treated as the same letter.
Finding Palindromes Inside a Text
In Find mode the checker reads the text three ways. It lists every palindromic word at or above the length you set, counting repeats. It lists sentences, split at full stops, question marks, exclamation marks and line breaks, that are palindromes. And it reports the longest palindromic stretch anywhere in the letters, shown with its original spacing and punctuation. That last search uses Manacher's algorithm, which takes time proportional to the length of the text, so a long document is no slower per letter than a short one.
Take "Anna and Bob saw a kayak at noon. Was it a car or a cat I saw? Wow, wow, wow." With a minimum of three letters the words are kayak, anna, noon, bob, and wow (three times). Two sentences are palindromes — Was it a car or a cat I saw? and Wow, wow, wow. — and the longest stretch is Was it a car or a cat I saw, at 19 letters.
Palindromes and Numbers
Digits count as characters, so 12321 is a palindrome and 12345 is not. With punctuation ignored, a figure written as 1,221 is checked as 1221. For properties of a number beyond palindromes, such as whether it is square or triangular, use the Number Properties Calculator.
Frequently Asked Questions
- What is a palindrome?
- A word, number, or phrase that reads the same forwards and backwards, such as kayak, 12321, or "Never odd or even". For phrases the convention is to ignore spaces, punctuation, and capitals and compare the letters alone.
- Does punctuation count?
- Not by default, because that is how sentence palindromes are judged. "Was it a car or a cat I saw?" only works once the spaces and the question mark are set aside. Untick Ignore spaces and punctuation if you want a strict character-by-character test.
- Is a single letter or number a palindrome?
- Yes: it reads the same in both directions, so a and 7 pass. Empty text does not, because there is nothing to compare, and the checker says so rather than calling it a palindrome.
- What is the longest palindrome word in English?
- In ordinary dictionaries the longest common one is redivider, at nine letters. Tattarrattat, 12 letters, was coined by James Joyce in Ulysses and appears in the Oxford English Dictionary. Finnish has the 19-letter saippuakivikauppias, meaning a soapstone seller.
- How do I check a number?
- Type it in the box; digits are compared like letters. To see whether numbers in a list are palindromes, put one per line and read the line-by-line table.
- What is the difference between letters and whole words?
- Letters mode reverses the text character by character. Whole words mode reverses the order of the words and compares them: "Fall leaves after leaves fall" reads the same word by word, even though its letters reversed spell something else.
- Is my text sent anywhere?
- No. The check runs entirely in your browser; nothing is uploaded or stored.