Palindrome Checker
Check if words, phrases, or sentences are palindromes and identify the longest palindromic substring within your text.
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Use this online palindrome checker to analyze words, phrases, sentences, or paragraphs for symmetry. The tool determines whether your entered text reads the exact same forward and backward. When evaluating the entire input, the checker applies a standard normalization step by converting all ASCII letters to lowercase and ignoring spaces, punctuation marks, and non-alphanumeric symbols. This allows classic phrases like "A man, a plan, a canal: Panama" or single characters to be accurately recognized as palindromes.
Beyond testing the full input, the tool scans for contiguous palindromic sequences within longer text passages and extracts a longest palindromic portion while preserving its original casing and punctuation. It also examines individual words longer than one character across your text to identify specific palindromic terms. If you leave the input field empty, the tool treats the input as non-palindromic. Enter any text string to inspect overall symmetry, discover internal palindromic substrings, and review matching terms instantly.
Instructions
- Enter or paste your text into the Text area.
- Click the submit button to analyze the input.
- Review the overall palindrome classification to see whether the complete text reads symmetrically.
- Inspect the identified longest palindromic portion and any detected palindromic words listed in the output.
Examples
- Check the phrase "A man a plan a canal Panama" to confirm that spaces and letter casing are normalized during whole-phrase validation.
- Paste a paragraph containing words like "racecar", "level", and "noon" to extract individual palindromic terms and find the longest symmetrical sequence.
FAQ
How does the tool determine if a whole sentence is a palindrome?
For whole-text evaluation, the tool converts ASCII letters to lowercase and discards all spaces, punctuation marks, and non-alphanumeric characters before comparing the text with its reverse.
Are spaces and punctuation removed when finding the longest palindromic portion?
No. When searching for the longest contiguous palindromic portion, character matching is case-insensitive, but spaces, punctuation, and original characters remain part of the substring.
What happens if the text input is left blank?
An empty input is accepted by the tool and is classified as not a palindrome.
Does a single character count as a palindrome?
Yes. A single character reads identically forward and backward, so it is classified as a palindrome.