Palindrome checker
Check if a word, phrase or sentence reads the same forwards and backwards. Results appear as you type.
Type or paste any word, phrase or number above to check if it is a palindrome.
The history of palindromes
The word palindrome comes from the Greek palin dromos — "running back again" — and was coined in English by the playwright Ben Jonson in the 1600s, but the wordplay itself is far older. The most famous ancient example is the Sator Square, a five-word Latin palindrome (SATOR AREPO TENET OPERA ROTAS) found scratched into the ruins of Pompeii, meaning it predates 79 AD. Greek and Latin writers composed palindromic verse as displays of skill, and the fascination never faded: palindromes now appear in puzzles, programming interviews, calendar curiosities like 02/02/2020, and even molecular biology, where palindromic DNA sequences read the same on both strands and mark the sites where enzymes cut.
Palindromes in programming
Checking whether a string is a palindrome is one of the most common introductory programming exercises. It tests understanding of string manipulation, indexing, and comparison. The naive approach compares the string to its reverse. A more efficient approach uses two pointers starting at each end and moving toward the center, stopping if a mismatch is found. Palindrome checking appears in technical job interviews at software companies as a basic algorithm question — this checker performs the same normalization step (strip punctuation, lowercase everything) that most interview solutions are expected to include.
Frequently asked questions
What is a palindrome?
A palindrome is a word, phrase, number or any sequence that reads the same forwards and backwards. "Racecar" is one: r-a-c-e-c-a-r is identical from either end. Phrases qualify too, under the convention that spaces, punctuation and capitalization are ignored — "A man, a plan, a canal: Panama!" collapses to "amanaplanacanalpanama", which mirrors perfectly. Type any word or sentence into the checker above and it applies exactly this test instantly.
Does the palindrome checker ignore spaces and punctuation?
By default, yes — the checker strips spaces and punctuation and lowercases everything before comparing, which is the classical definition used for phrase palindromes. Enable Strict mode to compare the exact characters as typed instead: in strict mode "racecar" still passes, but "Racecar" fails on the capital R and "A man a plan a canal Panama" fails on its spaces. Strict mode is the right setting when you are checking symmetric character sequences in code or data rather than natural language.
What are some famous palindromes?
Single words: racecar, level, madam, radar, civic, kayak and noon. Among phrases, "A man, a plan, a canal — Panama!" is the celebrity, coined by British wordplay master Leigh Mercer in 1948. "Able was I ere I saw Elba" imagines Napoleon lamenting his exile; "Never odd or even", "Do geese see God" and "Was it a car or a cat I saw" round out the classics. Paste any of them into the checker to watch the normalization at work.
Can numbers be palindromes?
Yes — 121, 1331 and 12321 all read the same in both directions, and every single-digit number is trivially palindromic. Mathematicians study them seriously: take almost any number, reverse it and add, repeat, and you usually reach a palindrome (89 takes 24 steps to reach 8813200023188). Whether the number 196 ever gets there is a famous unsolved question. Palindromic dates like 02/02/2020 — which read the same in every date format — draw wide attention when they occur.
What is the longest palindrome word in English?
"Tattarrattat" — James Joyce's invented word for a knock on the door in Ulysses — runs 12 letters and is cited by Oxford as the longest in literature. Among more conventional words, "detartrated" (11 letters, a chemistry term) and "redivider" or "rotavator" (9 letters each) lead the list. Other languages do better: Finnish offers "saippuakivikauppias", a 19-letter word for a soapstone seller, often cited as the world's longest everyday palindromic word.