Palindrome Checker

How to use Palindrome Checker

1. Type or paste a word, phrase or sentence.
2. The verdict appears immediately, with the cleaned string it actually tested.
3. Check the word list underneath for individual palindromic words inside longer text.
4. Case, spaces and punctuation are ignored; letters and digits are all that count.
5. Single letters are technically palindromes but are excluded from the word list as noise.
6. Accented characters are not folded, so “é” and “e” are treated as different letters.

What counts, and what is ignored

The check strips everything except letters and digits, then lowercases the rest, so “A man, a plan, a canal: Panama” reads as amanaplanacanalpanama and passes. That is the standard convention for phrase palindromes — punctuation and word boundaries are treated as typography rather than content. A strict character-for-character check, which would fail that phrase on the comma alone, is rarely what anyone means.

Palindromes worth knowing

The shortest interesting ones are everyday words: level, rotor, kayak, racecar, deified. The famous phrases are “A man, a plan, a canal: Panama” and “Never odd or even”. Napoleon is supposed to have said “Able was I ere I saw Elba”, which he did not. Numeric palindromes matter in programming interviews and in recreational mathematics — the Lychrel problem asks whether repeatedly reversing and adding a number always eventually produces a palindrome, and for 196 nobody knows.

Why programmers keep meeting this problem

Palindrome checking is the standard first exercise for two-pointer technique: walk one index from each end, compare, move inward. It runs in linear time with constant extra space, unlike the obvious reverse-and-compare, which allocates a second copy of the string — exactly what this tool does, because for text a person typed the difference is irrelevant. Interviewers like it because the naive answer is correct but not optimal, which gives the conversation somewhere to go.