Palindrome Checker

What Is a Palindrome?

A palindrome is a word, phrase, number, or sequence that reads the same forwards as it does backwards, once spaces, punctuation, and capitalisation are ignored. Simple examples include "level," "radar," and "civic." More impressive are palindromic phrases like "A man, a plan, a canal, Panama" or "Was it a car or a cat I saw?" — sentences that remain identical when reversed at the character level, ignoring spacing and punctuation.

How This Checker Works

The tool strips out spaces, punctuation, and capitalisation differences, then compares the cleaned string against its own reverse. If they match exactly, character for character, it's a palindrome. This is the standard definition used in linguistics and recreational mathematics — the underlying letter sequence must be symmetric, even though the way it's written (spacing, capitals) doesn't need to be.

Palindromes in Numbers and Dates

Palindromes aren't limited to words — numbers can be palindromic too, like 12321 or 909. Palindromic dates (where the digits read the same both ways, e.g. 02/02/2020) attract public attention when they occur because they're relatively rare. Palindromic numbers also appear in mathematical curiosities, such as the study of numbers that become palindromes after repeated reversal-and-addition.

Frequently Asked Questions

Does capitalisation matter?

No — this checker treats uppercase and lowercase letters as equivalent, following the standard convention for palindrome checking, since "Racecar" is considered just as valid a palindrome as "racecar."

Do spaces and punctuation count?

They're ignored for the purposes of checking, which is why full sentences like "A man, a plan, a canal, Panama" qualify as palindromes — the individual letters are symmetric even though the word breaks aren't mirrored.

What's the longest known palindrome?

In natural language, meaningful palindromic sentences longer than a few words are rare and impressive linguistic constructions. In pure number or symbol sequences, "longest palindrome" isn't meaningfully bounded — arbitrarily long symmetric sequences can always be constructed.