palindrome-checker
A palindrome checker tests whether a string reads the same forwards as backwards — like "racecar", "level", or "A man a plan a canal Panama" — supporting natural-language palindromes that ignore case, spaces, and punctuation, plus strict-mode for exact character equality. The ZTools Palindrome Checker handles single words, phrases, full sentences, numbers (12321 is a palindrome), and even multi-word literary palindromes; shows the normalized comparison so users see exactly which characters were compared; and reverses the input as a separate output for quick reverse-text needs.
Use cases
Wordplay, crosswords, and puzzles
Quick check whether "kayak", "deified", or "rotator" is a palindrome. Useful for crossword construction and word-game prep.
Number palindrome puzzles
"Is 12321 a palindrome?" Yes. "12345?" No. Frequent in math contests and number-theory exercises. The checker handles digits as readily as letters.
Date palindromes (e.g., 02/02/2020)
Some dates read the same forwards and backwards. Test "20020220" or "1991/19/91" formats to find calendar palindromes.
Programming exercise validation
"Write a function to check if a string is a palindrome" is a classic interview question. Use the checker to verify your function output against many test cases.
How it works
- Type or paste the text — Any length. Words, phrases, sentences, or numbers all supported.
- Pick the comparison mode — "Loose" (default): ignore case, spaces, punctuation — the natural-language mode. "Strict": exact character-by-character equality including case and punctuation.
- Read the verdict — Either "Palindrome" or "Not a palindrome". For the latter, the differing characters are highlighted in both the original and the reversed string.
- See the normalized form — When using loose mode, the tool shows the cleaned version that was compared (lowercase, no spaces, no punctuation) so the comparison is transparent.
Examples
Input: "racecar"
Output: Palindrome ✓ — strict mode
Input: "A man, a plan, a canal: Panama"
Output: Palindrome ✓ (loose), normalized: "amanaplanacanalpanama"
Input: 12321
Output: Palindrome ✓
Frequently asked questions
What is a palindrome?
A string that reads the same forwards and backwards. "Madam", "noon", "12321", and "race car" are palindromes. The strict-mode definition requires exact character match; the loose definition (more common in literature) ignores case, spaces, and punctuation.
Are punctuation and spaces considered?
Default is "loose" — punctuation and spaces are ignored, matching the way humans normally read palindromes. Switch to "strict" if you need exact symbol-by-symbol equality.
Are numbers palindromes?
Yes if they read the same forwards and backwards: 1, 11, 121, 1221, 12321. Most prime numbers aren't palindromes; many years (e.g., 2002) are.
What's the longest known palindrome?
In English, "tattarrattat" (12 letters, coined by James Joyce in Ulysses) is one of the longest single-word palindromes in dictionaries. Phrase palindromes can be arbitrarily long; one famous example exceeds 17,000 letters.
Are palindromes important in coding interviews?
Yes — "is this a palindrome?" is a classic question because it tests string handling, two-pointer technique, and edge cases (empty string, single character, even/odd length). The checker is a quick way to validate solutions.
Tips
- For sentence palindromes, always use loose mode — even famous palindromes like "Madam, I'm Adam" need normalization.
- Number palindromes are sometimes called "numerical palindromes" — same concept as letters.
- Palindromic dates (DDMMYYYY or MMDDYYYY) are a fun way to find rare calendar events.
- In genetics, palindromic DNA sequences (read the same on both strands) are biologically significant — different definition but same intuition.
Try it now
The full palindrome-checker runs in your browser at https://ztools.zaions.com/palindrome-checker — no signup, no upload, no data leaves your device.
Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub